lENCE    OF 
HYGIENE 


W:C.C.PAKES  ^AXNANKIVELL 


PAUL  B.HOFBEH 

MEDICAL  BOOKS 

69Z.5  9thSt-.iV.\. 


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in  tl|p  ffltt^  of  N^m  fork 

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THE  SCIENCE  OF  HYGIENE 


Digitized  by  the  Internet  Archive 

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http://www.archive.org/details/scienceofhygieneOOpake 


THE 
SCIENCE  OF  HYGIENE 

A  TEXT-BOOK  OF  LABORATORY  PRACTICE 
FOR  PUBLIC  HEALTH  STUDENTS 

BY 

WALTER    C.    G.    PARES 

D.P.H.  (CAMB.),   F.I.C. 

LATE    DEMONSTRATOR   OF   SANITARY   SCIENCE    AND    BACTERIOLOGIST   TO 
guy's    HOSPITAL,    ETC.    ETC. 


NEW     EDITION 
REVISED    BY 

A.   T.    NANKIVELL 

M.D.  (state   medicine),  B.S.   LONB.,  D.P.H.  (CAMB.),  ETC. 

DEMONSTRATOR   OF    PUBLIC   HEALTH,    KINg's   COLLEGE, 
UNIVERSITY   OF    LONDON 


NEW   YORK 

D.  VAN  NOSTRAND  COMPANY 

T\\^ENTY-F1VE   PARK   PLACE 

1912 


\^         %^h. 


'b-  -• 


■?  1 1 


PREFACE  TO  THE  REVISED  EDITION 

THIS  book  is  intended  for  the  use  of  students  who  are  work- 
ing for  a  diploma  in  public  health ;  and  it  is  hoped  that 
they  will  find  it  useful  not  only  before  their  examinations,  but 
afterwards,  should  they  happen  to  work  again  in  public  health 
laboratories. 

When  I  was  working  for  my  D.P.H.  I  found  the  first  edition 
of  Dr.  Pakes'  book  more  valuable  than  any  other  text-books  on 
laboratory  work :  the  arrangement  of  the  subject  matter  was 
simple  and  concise,  there  was  no  unnecessary  overlapping,  and 
what  the  Author  had  to  say  he  said  plainly  and  directly.  I  have 
tried,  in  this  new  edition,  to  attain  the  same  standard  of 
excellence. 

i\ll  the  practical  laboratory  work,  apart  from  bacteriological 
methods,  required  by  D.P.H.  students,  is  included  in  this 
volume ;  and  no  effort  has  been  spared  to  make  the  book  com- 
plete. Many  modern  text-books  have  been  consulted ;  but 
nothing  has  been  merely  transferred  from  these. 

The  first  edition  of  this  book  contained  chapters  on  physics, 
bacteriology,  and  vital  statistics.  It  was  felt,  however,  that  such 
subjects  were  better  treated  in  other,  and  necessarily  larger, 
books ;  and  that  much  of  these  sciences  could  hardly  be  con- 
sidered as  laboratory  work.  For  these  reasons,  no  part  of  this 
volume  is  devoted  to  these  subjects. 

On  the  other  hand,  many  additions  have  been  made,  and  much 
of  the  text  has  been  re-written. 


vi  THE   SCIENCE    OF   HYGIENE 

The  illustrations  in  this  volume,  which  appeared  also  in  the 
first  edition,  are  the  admirable  work  of  Dr.  T.  G.  Stevens. 

My  thanks  are  especially  due  to  Dr.  A.  J.  Malcolm,  my  fellow- 
demonstrator  in  the  Public  Health  Laboratories  of  King's  College, 

for  his  help  and  suggestions. 

A.  T.  N. 

King's  College 

University  of  London 


CONTENTS 


Water  Analysis 

I 

Interpretation  of  Results  . 

35 

Standard  Solutions 

59 

Milk  Analysis  . 

65 

Butter  Analysis 

75 

Flour  Analysis 

S3 

Bread  Analysis 

85 

Coffee  Analysis 

87 

Spirits  Analysis 

89 

Wines  Analysis 

91 

Beer  Analysis 

92 

Vinegar  Analysis 

93 

Analysis  of  Air 

95 

Analysis  of  Soil 

106 

Disinfectants   . 

III 

Microscopy 

.     116 

Meat  Inspection 

.     146 

Appendix 

.     159 

Index  . 

.     162 

Vll 


LIST  OF  ILLUSTRATIONS 


FIG. 

I. 

Hempel's  Bulb 

2. 

Wheat  Starch 

3. 

Barley         ,, 

4- 

Rye 

5- 

Potato         ,, 

6. 

Arrowroot,, 

7. 

Pea               ,,     .       . 

8. 

Bean             ,, 

9- 

Maize            „ 

10. 

Rice              ,, 

II. 

Oat 

12. 

Sago             ,, 

13. 

Tapioca        ,, 

14. 

Calandra  Granaria 

15- 

ACARUS   FARINy^i 

16. 

Bruchus  Pisi 

17. 

Tylenchus  Tritici  . 

18. 

Penicillium  Glaucum 

19. 

Aspergillus 

20. 

MUCOR 

21. 

Peronosporon 

22. 

PUCCINIA       . 

23. 

USTILAGO   SEGETUM     . 

24. 

Tilletia  Caries 

25. 

>>            >>            • 

26. 

Claviceps  Purpurea 

27. 

>>                  »>                      • 

28. 

Butter 

29. 

Margarine 

30. 

Coffee 

PAGE 
96 
118 
118 
118 
119 
119 
119 
119 
119 

120 
120 
121 
121 
121 
121 
122 
122 
123 
124 
124 

125 
126 
126 
126 
127 
127 
128 
128 
129 


ly 


X 

ihlii    bLllJ.iNClL 

FIG. 

31. 

Chicory 

32. 

>>           •               •               • 

33. 

Tea 

34. 

>>                 ... 

35. 

Cocoa 

36. 

Cotton 

37. 

Linen 

38. 

Jute 

39- 

Hemp 

40. 

Wood 

41. 

Wool 

42. 

Silk 

43- 

PULEX  Irritans 

44. 

Pui.Ex  Penetrans     . 

45- 

CiMEX 

46. 

Pediculus  Capitis    . 

47. 

Pediculus  Vestimentorum    . 

48. 

Pediculus  Pubis 

49. 

AcARus  Scabei 

50- 

Ixodes  Ricinus 

51- 

Diatoms 

52. 

Desmids 

53. 

Vorticella 

54. 

Euglena  Viridis 

55. 

Spirogeira  . 

56. 

Beggiatoa  . 

57. 

VOLVOX 

58. 

Ulothrix    . 

59. 

Human  Hair 

60. 

Dog's  Hair 

61. 

Cow's  Hair 

62. 

Rabbit's  Hair 

63. 

Amceba 

64. 

Paramoecium 

65. 

Daphnia 

66. 

Ova  of  Worms 

67. 

Trichina  Spiralis    . 

6S. 

>i               >i          • 

FIG. 
69. 
70. 

72. 
11' 

75. 
76. 

77. 
78. 

79. 
80. 


LIST   OF    ILLUSTRATIONS 
T/ENiA  Mediocanellata 


BOTHRIOCEPHALUS    LATUS 


DiSTOMA   HePATICUM 


XI 

PAGB 

153 

158 
158 
158 
158 
158 


THE  SCIENCE  OF  HYGIENE 


WATER  ANALYSIS 

COLLECTION   OF   SAMPLES 

In  collecting  samples  of  water  for  chemical  analysis,  attention 
should  be  paid  to  two  points  :  first,  to  the  cleanliness  of  the 
vessel  in  which  the  water  is  to  be  collected ;  and,  secondly,  to 
the  actual  sample  itself.  With  regard  to  the  first,  a  glass- 
stoppered  Winchester  quart  bottle  is  by  far  the  best  for  a  collect- 
ing vessel :  this  bottle  should  be  thoroughly  cleansed.  It 
should  be  well  rinsed  with  strong  sulphuric  acid,  subsequently 
with  distilled  water  until  all  trace  of  acid  has  disappeared,  and 
finally  with  ammonia-free  water.  The  stopper  should  be  replaced 
and  tied  down  but  ?iof  scaled.  In  actually  collecting  the  samples 
the  bottle  should  first  be  filled  with  the  water  to  be  collected  and 
emptied,  and  this  should  be  done  a  second  time.  After  this  a 
true  sample  should  be  allowed  to  run  in  the  bottle  if  collected 
from  a  tap,  or  the  bottle  should  be  sunk  into  the  water  so 
that  the  mouth  is  about  two  inches  below  the  surface  if  collected 
from  a  reservoir  or  river.  The  water  should  not  fill  the  bottle, 
but  should  come  just  above  the  shoulder.  In  sending  the  water 
to  a  laboratory  for  examination,  it  is  convenient,  after  having 
replaced  the  glass  stopper  and  tied  it  down,  to  place  the  bottle  in 
the  well-known  baskets  made  for  that  purpose. 

With  regard  to  the  second  point,  the  actual  collection  of  the 
sample,  it  should  be  borne  in  mind  that  the  sample  should  really 
be  one  to  test  the  potentiality  for  evil  of  the  water  in  question. 
For  instance,  if  the  water  is  suspected  of  containing  lead,  it 
would  be  obviously  unfair  to  send  for  analysis  the  water  which 
has  been  standing  for  some  hours  in  lead  pipes,  since  the  con- 
sumers do  not  drink  this  water  as  a  matter  of  common  practice. 


2  WATER   ANALYSIS 

In  other  words,  in  order  to  collect  a  water  sample  for  examina- 
tion, that  sample  should  be  such  as  is  ordinarily  consumed. 

If  the  water  be  one  from  a  reservoir  or  tank,  it  should  be 
collected  as  it  is  flowing  from  such  reservoir  or  tank  into  the  mains. 

In  the  case  of  a  well  water  the  same  would  hold,  that  is  to  say, 
the  pipe  should  not  be  emptied  of  the  water  if  this  is  not  done 
as  a  matter  of  ordinary  practice. 

It  sometimes  happens  that  owing  either  to  a  leaden  or  leaky 
pipe,  the  water  from  a  well  may  be  quite  good  as  it  comes  from 
the  well,  but  bad  as  it  is  delivered.  In  this  case  it  may  be 
necessary  to  examine  samples  of  the  water  collected  from  both 
ends  of  the  pipe.  Again,  the  tap  is  sometimes  contaminated,  and 
it  may  be  necessary  to  clean  that  thoroughly  before  collecting  the 
samples. 

In  the  case  of  a  river  it  is  obvious  that  the  water  may  be  taken 
from  either  above  or  below  any  sources  of  contamination  or 
pollution  that  may  flow  into  the  river.  If  therefore  we  wish  to 
analyse  such  a  water,  it  must  be  taken  into  consideration  whence 
the  water  from  the  river  is  usually  removed  for  drinking  purposes. 
For  example,  if  the  intake  of  a  company  is  at  a  certain  point  in 
the  river  the  sample  should  be  collected  at  a  point  as  near  the 
actual  intake  as  possible. 

The  water  should  be  examined  as  soon  after  collection  as 
possible,  as  there  is  no  doubt  that  changes  do  occur  after  a  lapse  of 
a  short  time  only,  in  the  water  kept  even  in  a  well-stoppered  bottle. 

This  is  especially  the  case  with  unstable  waters,  such  as 
sewage  effluents,  or  superficial  wells  liable  to  pollution.  If  the 
water  therefore  has  to  be  transmitted  a  considerable  distance  it 
is  advisable,  wherever  possible,  to  surround  the  Winchester  quart 
with  ice.  By  doing  so  the  changes  in  the  water  are  retarded,  and 
the  water  as  analysed  is  practically  the  water  as  collected. 

The  bottle  should  have  a  label  attached  to  it.  The  label 
should  bear  the  following  particulars : — 

1.  The  name  and  address  of  sender. 

2.  The  date  of  collection  of  the  sample. 

3.  Source  of  water  (river,  well,  etc.). 

If  the  water  is  from  a  well,  further  details  should  be  added  to 
the  above : — 

1.  The  Depth  of  the  well. 

2.  The  nature  of  the  Geological  formation  from  which  the 
water  is  obtained. 


WATER    REPORT  3 

3.  Proximity  to  Sea  or  Tidal  River. 

4.  Proximity  of  Drains,  Cess-pools,  Manured  Lands,  or  collec- 
tions of  decaying  organic  matter. 

5.  Any  other  details  which  may  seem  to  bear  upon  the  purity 
of  the  sample. 

WATER   REPORT 

A  chemical  water  report  should  contain  a  statement  of  the 
salts  and  organic  material  present  in  the  water.  These  figures, 
while  they  afford  evidence  as  to  possible  pollution,  either  recent 
or  remote,  enable  us  to  judge  of  the  general  fitness  of  the  water 
for  drinking  or  domestic  purposes. 

A  considerable  amount  of  confusion  has  been  caused  by  the 
fact  that  different  analysts  return  their  results  in  different  forms. 
It  will  be  understood  that  the  amount  of  these  materials  must, 
in  a  sample  of  water,  be  extremely  small.  In  order  therefore  to 
state  the  results  without  necessitating  the  use  of  fractions  of  a 
milligram,  it  is  usual  to  express  results  as  parts  per  100,000, 
per  1,000,000,  per  100,000,000,  or  in  grains  per  gallon.  It  may 
be  stated  that  there  are  advantages  in  each  of  these  methods. 
In  England  a  fairly  large  number  of  analysts  still  return  their 
results  in  grains  per  gallon.  On  the  Continent,  however,  it  is 
universally  the  case  that  they  are  reported  either  in  parts  per 
100,000  or  in  parts  per  1,000,000.  It  will  be  seen  therefore  that 
reports  expressed  in  parts  per  100,000  can  be  compared  with  the 
Continental  reports  without  previously  converting. 

It  is  sometimes  the  custom  to  express  the  ammonia  in  parts 
per  1,000,000  or  in  parts  per  100,000,000,  while  the  rest  of  the 
report  is  expressed  in  parts  per  100,000.  This  method  is  adopted 
in  order  that  the  ammonia  should  be  returned  in  units  and  not 
in  decimals,  but  the  disadvantage  of  having  two  forms  of  return 
in  the  same  report  would  appear  to  be  greater  than  that  of 
having  the  ammonia  expressed  in  decimals.  If  one  accustoms 
oneself  to  the  quantities  expressed  in  parts  per  100,000,  it  is 
merely  a  matter  of  remembering  that  0*005  is  the  limit  instead 
of  5.  In  the  following  pages,  therefore,  the  results  will  all  be 
tabulated  in  parts  per  100,000. 

When  a  report  is  expressed  in  grains  per  gallon  and  it  is 
necessary  to  convert  these  figures  into  parts  per  100,000,  it  is 
obviously  only  necessary  to  multiply  these  results  by  ^^.  If, 
on  the  other  hand,  we  require  to  convert  parts  per  100,000  into 


4  WATER   ANALYSIS 

grains  per  gallon,  it  is  necessary  only  to  multiply  by  o'7.  The 
reasons  for  this,  of  course,  are  that  there  are  100,000  grammes  in 
100,000  c.c.  and  70,000  grains  in  a  gallon. 


PHYSICAL  CHARACTERS 

Before  proceeding  to  the  analysis  of  the  water  by  the  various 
chemical  methods  which  are  adopted,  it  is  generally  necessary  to 
make  some  preliminary  observations  on  the  physical  characters  of 
the  sample. 

1.  Turbidity.  Waters  vary  somewhat  in  the  amount  of 
turbidity  they  show,  although  as  a  rule  the  best  waters  are  per- 
fectly clear.  It  is  of  course  possible  that  a  perfectly  safe 
drinking  water  might  have  been  rendered  turbid  through  the 
shaking  up  with  it  of  some  mineral  matter,  but,  speaking  generally, 
a  water  that  shows  any  marked  turbidity  will  prove,  upon 
further  examination,  to  be  unfit  for  drinking  purposes.  One 
expresses  the  degrees  of  turbidity  as  "  clear,"  "  slightly  turbid," 
or  "very  turbid,"  the  last  applying  more  especially  to  sewage  or 
sewage  effluents. 

2.  The  next  point  to  be  considered  is  the  colour. 

In  order  to  determine  the  colour  it  is  necessary  first  of  all  to 
allow  any  sediment  to  deposit.  The  clear  supernatant  water  is 
then  poured  into  what  is  known  as  a  two-foot  tube.  This  consists 
of  a  glass  cylinder,  at  each  end  of  which  a  piece  of  plate  glass 
is  screwed.  When  the  water  is  poured  in,  the  plate  which  has 
been  removed  in  order  to  allow  of  this  should  be  screwed  down, 
and  the  whole  apparatus  carefully  wiped.  The  eye  should  then 
be  placed  at  one  end,  and  at  the  other  a  white  porcelain  slip  or 
piece  of  paper.  Good  waters  are  generally  slightly  blue  when 
seen  through  this  tube;  if  there  is  any  yellowish  or  brownish 
colour,  there  will  be  some  suspicion  of  sewage  contamination 
unless  the  water  happens  to  have  been  collected  from  a  peaty 
soil.  Occasionally  the  water  possesses  a  decidedly  green  colour 
owing  to  the  presence  of  the  green  alga^,  which  are  of  course,  in 
themselves,  harmless. 

3.  Taste.  This  is  by  no  means  a  valuable  test ;  the  pleasant 
taste  of  a  water  is  generally  due  to  the  solution  of  gases,  and 
even  the  best  of  waters  when  not  aerated  are  insipid.  When  it 
is  remembered  that  a  smaller  quantity  of  sodium  chloride  than 
75  grains  to  the  gallon  or  100  grammes  to  the  100,000  cannot  be 


PHYSICAL   CHARACTERS  5 

tasted,  it  will  be  seen  of  what  little  worth  the  taste  is.  Some 
algas,  however,  when  they  decompose  liberate  volatile  oils,  of 
which  even  a  trace  may  cause  a  water  to  taste  and  smell  unplea- 
santly. Such  algae  are  found  chiefly  in  reservoirs  and  filter  beds  : 
their  decomposition  products,  although  they  make  the  water 
objectionable,  do  not  seem  to  make  it,  in  any  way,  dangerous  to 
health. 

4.  Smell.  A  good  drinking  water  should,  of  course,  be 
absolutely  inodorous.  If  there  is  a  marked  degree  of  contamina- 
tion, or  the  water  has  been  collected  from  a  peaty  soil  or  from 
the  neighbourhood  of  some  dye  or  chemical  works,  it  is  possible 
that  the  water  may  possess  some  odour.  It  by  no  means  follows, 
however,  that  a  water  which  is  so  contaminated  as  to  be  utterly 
unfit  to  drink  possesses  any  odour  at  all. 

In  order  to  detect  the  odour,  the  most  convenient  method  is  to 
place  about  250  c.c.  in  a  glass-stoppered  bottle,  which  is  then 
placed  in  a  water  bath  or  oven  at  about  30°  C.  for  a  few  minutes. 
The  stopper  should  then  be  removed  and  the  nose  applied  to  the 
bottle  at  once.  This  is  necessary,  since  the  odour  is  extremely 
evanescent. 

5.  As  has  been  before  stated,  a  palatable  water  is  well 
aerated.  In  order  to  test  this  properly  it  is  generally  only 
necessary,  to  pour  some  of  the  water  into  an  open  beaker,  and 
notice  the  evolution  of  small  bubbles  of  gas.  This  test  is  of  no 
value  as  regards  the  fitness  of  the  water  for  drinking  purposes, 
but  is  merely  evidence  of  its  palatability. 

6.  Reaction.  The  reaction  of  most  drinking  waters  is 
alkaline.  Occasionally  a  drinking  water  is  found  to  be  acid,  and 
is  then  held  not  to  be  suitable  for  a  water-supply  because  of  the 
facility  with  which  it  takes  up  lead.  This  has  been  found  to  be 
the  great  objection  to  the  Yorkshire  moor  supply  for  Sheffield, 
etc.  Such  a  water  derived  from  peaty  soil  contains  humic  and 
ulmic  acids.  The  alkalinity  or  acidity  of  a  water  in  itself  is  no 
criterion  of  the  pollution  of  the  water  by  sewage,  since  most 
waters  which  are  highly  contaminated  by  sewage  still  retain  their 
alkalinity.  The  waters  drawn  from  the  neighbourhood  of  dye  or 
chemical  works  are  sometimes  acid,  but  other  criteria  of  their  un- 
suitability  for  drinking  purposes  will  be  found  on  further  analysis. 

7.  The  Sediment.  As  has  been  before  stated,  a  good  water 
should  contain  no  sediment,  but  the  mere  presence  of  a  slight 
sediment  will  not  necessarily  condemn  the  water.  The  sediment 
may  consist  either  wholly    of  mineral   matter,   or  of  vegetable 


6  WATER   ANALYSIS 

matter,  or  of  both.     Its  nature  is  generally  discovered  by  micro- 
scopical examination,  and  will  be  treated  under  that  head. 


TOTAL    SOLIDS 

Apparatus  required 

1.  A  platinum  dish. 

2.  A  flask  graduated  at  200  c.c. 

3.  A  water  bath. 

4.  A  water  oven. 

5.  A  desiccating  chamber. 

6.  A  balance  which  will  turn  to  i  of  a  milligram. 

The  Process 

In  a  clear  water  with  no  sediment  it  is  obvious  that  the  solids 
will  be  those  in  solution.  In  turbid  waters  the  total  solids  may 
be  either  those  in  solution  plus  those  in  suspension,  or  those  in 
solution  alone.  Most  analysts  determine  the  total  solids  in 
solution ;  if,  therefore,  the  water  is  turbid,  it  must  be  allowed  to 
sediment,  or  must  be  filtered  before  proceeding  with  the  deter- 
mination. 

1.  200  c.c.  of  the  clear  water  should  be  measured  out  into  the 

graduated  flask. 

2.  The  platinum  dish  should  be  thoroughly  well  cleansed  with 

HCl,  and  subsequently  with  distilled  water ;  then  heated  in 
the  Bunsen  flame  and  placed  in  the  desiccator  over  H,jS04 
until  it  is  cold.  It  must  then  be  weighed,  and  a  note  of  its 
weight  taken. 

3.  Into  the  dish  as  much  of  the  200  c.c.  as  it  will  conveniently 

hold  is  poured.  The  dish  is  then  placed  over  a  water  bath 
and  covered  with  an  inverted  funnel  in  order  to  protect  the 
contents  from  the  dust.  From  time  to  time  more  water  is 
added  until  the  whole  of  the  200  c.c.  has  been  evaporated 
to  dryness. 

4.  The  dish  with  the  evaporated  contents  is  now  removed  from 

the  water  bath  and  placed  in  the  water  oven  and  kept  at 
100°  C.  for  from  20  minutes  to  half  an  hour. 

5.  Now   remove    the   dish    from    the  oven  and  place  it  in   the 

desiccator  over  H2SO4  until  it  is  cool. 

6.  Now  weigh  it  carefully  two  or  three  times,  replacing  it  in  the 

desiccator  for  5  or  10  minutes  between  each  weighing. 


TOTAL   SOLIDS  7 

Instead  of  heating  the  dish  in  the  water  oven  at  ioo°  C  some 
analysts  heat  it  in  an  air  oven  at  120°  C.  This  latter  method 
ensures  the  disappearance  of  the  water  of  crystallization  from  any 
of  the  salts  which  may  be  present  with  their  water  of  crystalliza- 
tion in  the  residue  evaporated  at  100°  C. 

EXAMPLE 

Weight  of  dish  ....     29-7834 

„       of  residue  of  200  c.c.  of  water  +  dish     30-0030 


Weight  of  residue      .  .  .  .0-2196 

.'.  Total  solids  per  100,000  =  0-2196  x  500=  109-800 

Notes 

If  it  is  necessary  to  determine  the  total  solids  in  a  short  time, 
a  less  quantity  of  water  than  200  c.c.  may  be  taken  ;  but  as  the 
residue  is  sometimes  only  very  small  the  error  of  experiment 
must  necessarily  be  greater.  In  a  sample  of  water  which  is 
known  to  be  very  hard,  or  to  be  very  saline,  100  c.c.  will  be 
ample. 

LOSS    ON    IGNITION 

After  the  total  solids  have  been  ascertained,  the  platinum  dish 
containing  the  residue  is  heated  over  the  flame  of  a  Bunsen 
burner  to  a  white  heat  for  some  time,  allowed  to  cool  and  re- 
weighed.  The  loss  in  weight  is  then  recorded  as  Loss  on 
Ignition. 

Whilst  the  solids  are  being  ignited,  blackening  will  take  place 
if  much  organic  matter  is  present,  and  this  fact  should  be  noted. 

The  loss  on  ignition  represents  to  a  large  extent  the  organic 
matter  present,  since  the  ignition  causes  this  to  be  oxidized,  and 
CO2  and  H2O  to  be  given  off.  It  is  not,  however,  altogether 
a  measure  of  the  amount  of  organic  matter,  since  the  water  of 
crystallization  and  the  ammonium  salts  are  also  driven  off. 

EXAMPLE 

Weight  of  dish -I- total  solids  .  .     30*0030  grammes 

„  ,,    -t- total  solids  (after  ignition)     29*9939     ,, 


Loss  on  ignition  (200  c.c.)      .         .  .      0*009 1  gramme 

.*.  Loss  on  ignition  per  100,000  =  4*55  grammes. 


8  WATER   ANALYSIS 

ESTIMATION    OF    CHLORIDES 

Apparatus,  etc.,  required 

1.  A  white  porcelain  evaporating  dish. 

2.  A  small  glass  stirring  rod. 

3.  A  50  c.c.  pipette. 

4.  A  burette  graduated  ino'i  c.c. 

5.  Potassium  chromate  solution. 

6.  Standard  silver  nitrate  solution. 

The  Process 

1.  Fill  the  burette  with  the  standard  silver  solution. 

2.  Measure  50  c.c.  of  the  water  to  be  examined  in  the  graduated 

pipette  and  run  it  into  the  white  evaporating  dish. 

3.  Add  one  or  two  drops  of  the  solution  of  KoCrO^  to  the  water 

and  stir. 

4.  Allow  the  silver  solution  to  run  into  the  water  drop  by  drop 

until  the  evanescent  brown  colour  remains, 
q.   Read  off  the  heiirht  of  the  solution  in  the  burette  and  note  it. 


'&' 


Explanation  of  the  Process 

When  a  solution  of  silver  nitrate  is  added  to  an  alkaline  solu- 
tion of  a  chromate  a  reddish  brown  precipitate  of  silver  chromate 
is  formed.  If,  however,  any  chloride  is  present,  the  silver  will 
combine  with  this  chloride  before  it  combines  with  the  chromate. 
The  interactions  taking  place  are  expressed  by  the  following 
equations  : — 

NaCl  +  AgNO.,  -  NaNO..  +  AgCl 
K,CrO,  +  2  AgNOa  ==  2KNO..  +  AgXrO^ 

When,  therefore,  the  permanent  brown  precipitate  is  formed,  all 
the  chloride  will  have  combined  with  the  silver,  and  the  amount 
of  the  silver  used  at  this  juncture  will  be  a  measure  of  the 
chlorides  present  in  the  water. 

EXAMPLE 

1st  reading  of  burette  .  .  .     6*6  c.c. 

2nd       „  „  ...     8-9    „ 

Amount  of  silver  used  .  .  •     2*3    ,, 


TOTAL   HARDNESS  9 

Now  I  c.c.  of  silver  nitrate  solution  =1     milligram  of  chlorine 

But  this  quantity  was  present  in  50  c.c.  of  the  water 

.'.  in  100  c.c.  there  will  be  4"6  milligrams  of  chlorine 

i.e.  there  will  be  4*6  parts  of  chlorine  in  100,000  parts  of  water. 

The  quantity  of  chlorine  is  frequently  expressed  in  terms  of 

NaCl  as  well  as  in  terms  of  CI  itself.     In  order  to  express  the  CI 

in  terms  of  NaCl  it  is  only  necessary  to  multiply  the  weight  of  CI 

by -^^—7^.     In  our  example  we  found  that  4*6  parts  of  CI  were 

present.     Expressed  as  NaCl  this  will  be  I'S^S  x  4*6  =  7'5  parts. 

Our  report  should  read  : — 

Chlorine       ....     4*6  parts  per  100,000 
Expressed  in  NaCl  .  .  •     7"5       j>  >» 

Notes 

The  estimation  should  always  be  repeated.  If  we  know  when 
to  expect  the  "end  point,"  we  are  able  to  estimate  more  easily 
the  exact  point  when  the  colour  changes. 

Before  filling  the  burette  it  must  be  scrupulously  clean.  A 
new  burette  should  be  washed  out  with  strong  sulphuric  acid 
and  subsequently  with  distilled  water  until  all  traces  of  the  acid 
have  disappeared.  After  it  is  clean,  a  few  c.c.  of  the  solution 
should  be  poured  in  and  (holding  it  horizontally)  allowed  to 
run  over  the  whole  of  the  surface.  The  burette  must  be  emptied 
and  filled  with  the  solution.  A  few  drops  must  now  be  allowed 
to  run  out,  in  order  to  fill  the  nozzle,  and  any  drop  which  hangs 
on  the  nozzle  must  be  removed.  The  height  of  the  fluid  in  the 
burette  must  be  carefully  read  and  noted.  In  the  case  of  colour- 
less fluids  it  is  customary  to  read  off  the  division  of  the  scale 
which  corresponds  to  the  bottom  of  the  meniscus.  In  the  case 
of  indigo,  however,  it  is  convenient  to  read  off  the  division  of 
the  scale  which  corresponds  to  the  top  of  the  meniscus. 

TOTAL   HARDNESS 
Apparatus,  etc.,  required 

1.  A  small  glass  stoppered  bottle  (about  125  c.c.  capacity). 

2.  A  burette  graduated  in  tenths  of  a  c.c. 

3.  An  Erlenmeyer  flask. 

4.  A  50  c.c.  pipette. 

5.  A  100  c.c.  measure  graduated  in  c.c. 

6.  Standard  soap  solution. 


10  WATER   ANALYSIS 

The  Process 

1.  Fill  the  burette  with  the  standard  soap  solution,  and  read  off 

the  height. 

2.  Measure  50  c.c.   of  recently  boiled  distilled  water  into  the 

bottle. 

3.  Add   o"5  c.c.   of  soap,   replace  the  stopper,  and  shake  the 

bottle  well.  Add  more  soap,  a  few  drops  at  a  time,  until  a 
permanent  lather  is  formed  after  brisk  shaking. 

4.  Read  off  the  height  of  the  soap  in  the  burette. 

The  difference  between  the  two  readings  will  be  the  amount 
of  soap  required  to  form  a  lather  with  perfectly  soft  water. 

{Note. — It  is  well  for  a  beginner  to  do  this  several  times  before 
he  begins  to  try  to  determine  the  hardness,  so  as  to  familiarize 
himself  with  the  appearance  of  a  permanent  lather,  and  in  order 
that  he  may  find  for  himself  the  amount  of  soap  which  must 
subsequently  be  deducted  from  that  used  to  form  a  lather  with 
the  water  under  examination.) 

After  having  done  this,  proceed  to  the  examination  of  the  water. 

1.  By  means  of  the  50  c.c.  pipette,  run  50  c.c.  of  the  water  into 

the  bottle. 

2.  Add  I  c.c.  or  less  of  the  standard  soap  at  a  time  to  the  water 

and  shake  well.  When  a  certain  amount  of  the  soap  has 
been  added,  the  lather,  which  is  at  first  very  transient, 
begins  to  remain  for  a  short  time.  When  this  point  has 
been  reached,  the  soap  must  be  added  only  a  few  drops  at 
a  time,  in  order  not  to  overshoot  the  mark. 

3.  When   sufificient  soap  has  been  added  the  bubbles  on   the 

surface  of  the  water  will  break  very  slowly ;  the  bottle 
should  then  be  laid  on  its  side  for  five  minutes.  If  at  the 
end  of  this  time  the  lather  is  still  present,  even  if  it  is 
diminished  in  thickness,  the  estimation  is  done,  and  it  only 
remains  to  read  off  the  height  of  the  soap  in  the  burette, 
and  deduct  from  it  the  height  observed  before  beginning 
the  estimation.  The  difference  will  be  the  amount  of  soap 
required,  and  from  this  is  calculated  the  hardness. 

Explanation 

A  soap  is  a  salt,  the  base  of  which  is  a  metal  and  the  acid  one 
of  the  fatty  acids.  Some  of  these  salts,  as  those  of  sodium  and 
potassium,  are  soluble  in  water,  and  when  rubbed  up  with  or 


TOTAL    HARDNESS  ii 

shaken  up  in  water  cause  a  lather.  Others,  such  as  those  of 
calcium  and  magnesium,  are  insoluble  in  water,  and  therefore  are 
precipitated ;  being  precipitated,  they  are  incapable  of  forming  a 
lather.  If  a  soluble  calcium  salt  is  present  in  water  and  a 
solution  of  a  sodium  soap  is  added^  the  insoluble  calcium  soap 
is  formed. 

The  cause  of  hardness  in  water  is  the  presence  in  it  of  soluble 
salts  of  calcium  and  magnesium.  So  long  as  either  of  these 
salts  exists  unprecipitated  in  the  water,  it  will  be  impossible  to 
form  a  lather.  Directly  they  have  been  precipitated  only  a 
slight  addition  of  soap  is  required  to  form  a  lather.  The  amount 
of  soap  required  to  form  a  lather  is  therefore  the  measure  of  the 
amount  of  the  salts  of  calcium  and  magnesium  present  in  the 
water. 

EXAMPLE 

It  was  found  that  it  took  o'8  c.c.  of  the  soap  solution  to  form 
a  lather  with  50  c.c.  of  distilled  water. 

The  sample  of  water  to  be  examined  took  7*6  c.c.  of  soap  to 
form  a  lather  with  50  c.c. 

50  c.c.  sample  required  .  .  -7*6  c.c.  soap 

50  c.c.  distilled      ,,         •  •  •     o'S     ,,      ,, 

Soap  solution  required  to  precipitate  Ca  and  Mg  salts  =  6  "8  c.c. 
But  I  c.c.  of  the  Standard  soap  solution  =  i  milligram  of  CaC03. 
.*.  50  c.c.  of  the  water  contain  6 "8  milligrams  of  Ca  and  Mg 
(expressed  as  CaCO;,). 

,'.   100  c.c.  of  the  water  contain  13*6  milligrams. 
In  other  words,  the  sample  has  a  hardness  of  13  6  parts  per 
100,000. 

Notes 

It  will  have  been  noticed  that  the  hardness  is  expressed  in 
terms  of  CaCOg,  whether  it  is  due  to  calcium  or  magnesium. 
This  is  merely  for  convenience,  so  that  one  need  only  have  one 
standard  solution.  As  a  matter  of  fact,  more  soap  is  required  to 
form  a  lather  with  a  certain  amount  of  magnesium  than  is  required 
for  an  equivalent  quantity  of  calcium. 

The  soap  solution  does  not  remain  permanently  of  the  same 
strength.  After  the  lapse  of  a  certain  time  it  undergoes  certain 
changes  and  becomes  weaker.  Unfortunately  this  change  does 
not  show  any  degree  of  constancy.  The  solution  may  remain  up 
to  standard  for  weeks,  and  then  suddenly  change. 

In  order,  therefore,  to  ascertain  the  hardness  of  any  sample 


12  WATER   ANALYSIS 

of  water  with  great   accuracy,  three  determinations   should   be 
made : — 

1.  The  soap  required  to  lather  50  c.c.  of  distilled  water. 

2.  The  soap  required  to  lather  50  c.c.  of  distilled  water  contain- 

ing 6  c.c.  of  the  standard  calcium  solution. 

3.  The  soap  required  to  lather  50  c.c.  of  the  sample. 

EXAMPLE 

No.  I  required    .     I'oc.c. 

No.  2         „         .     8-4  „ 

No.  3         „         .    15-6  „     (diluted  i  in  2  took  7 '8  c.c.) 

6  c.c.  Ca  solution  required     .     8*4- 1=    7*4  c.c. 

Hardness  in  sample     ,,  .    i5*6-i  =  i4'6    ,, 

But  7*4  c.c.  of  soap  solution  =  6  milligrams  of  CaCO.^. 

.'.   i4"6  c.c.         ,,  ,,        = — —  of  6  milligrams  of  CaCOg 

=  1 1  "8  milligrams  of  CaCOg. 
Thus  50  c.c.  of  the  sample  contain  ii-8     „  .    „ 

and  100  c.c.  „  „        23-6     „ 

.*.  100,000  parts  contain  23*6  parts  of  hardness,  expressed  as 
CaCOg. 

PERMANENT  HARDNESS 

Hardness  is  spoken  of  as  either  temporary  or  permanent.  The 
former  consists  of  calcium  bicarbonate  and  is  held  in  solution  by 
the  carbonic  acid  in  the  water.  When  the  carbonic  acid  is 
expelled  from  the  water  as  by  boiling,  the  bicarbonate  is  con- 
verted into  the  carbonate  and  is  at  the  same  time  precipitated, 
as  it  is  insoluble  in  water. 

Ca(HCO,).^  =  CaCOg  +  U,0  +  CO.. 

The  permanent  hardness  is  due  to  the  sulphates,  chlorides,  and 
nitrates  of  calcium  and  magnesium,  and  these  are  unaffected  by 
boiling. 

The  Process 

1.  Measure  100  c.c.  of  the  water  to  be  examined  in  a  graduated 

cylinder  and  pour  it  into  an  Erlenmeyer  flask. 

2.  Boil  over  a  piece  of  wire  gauze  until  the  bulk  is  reduced  to 

about  one-half. 

3.  Allow  it  to  cool  and  filter  through  a  hard  white  filter-paper 

which  has  been  well  washed  with  distilled  water. 


FREE    AMMONIA  13 

4.  Make  up  the  volume  to  100  c.c,  with  distilled  water. 

5.  Take  50  c.c.  of  this  and  estimate  the  hardness  as  before. 

This  estimation  is  also  expressed  in  terms  of  CaCO.. 
Having  estimated  the  total  and  the  permanent  hardness,  the 
difference  will  obviously  be  the  temporary  hardness. 

Notes 

The  hardness  is  expressed  in  grains  per  gallon  (degrees),  or  in 
parts  per  100,000  of  CaCOg.  Although  this  does  not  represent 
the  actual  truth,  since  other  salts  have  their  share  in  producing 
this  hardness,  it  is  an  expression  for  the  factor  of  practical 
importance,  i.e.  the  soap-destroying  power  of  the  water. 

In  laundry  work  the  whole  work  of  the  water  used  exercises  its 
soap-destroying  power,  and  it  is  only  when  the  soap  is  in  excess 
of  this,  that  the  detergent  action  of  the  latter  begins. 

It  v,'ill  occur  to  the  reader  that  in  washing  one's  hands,  only 
the  small  quantity  of  water  adhering  to  the  hands  need  affect  the 
soap,  before  a  lather  is  obtained.  Therefore  it  is  possible  to 
wash  the  hands  with  comfort  in  a  much  harder  water  than  can  be 
used  in  the  laundry  without  a  great  waste  of  soap. 


FREE   OR  SALINE  AMMONIA 
Apparatus,  etc.,  required 

1.  A  32-ounce  glass   retort,    or  a    long-necked    two-litre  glass 

flask. 

2.  A  condenser. 

3.  Clamps  and  burner. 

4.  12  Nessler  glasses  to  hold  100  c.c.  with  a  graduation  at  50  c.c. 

5.  White  glazed  porcelain  slab. 

6.  50  c.c.  burette  graduated  in  tenths  of  a  c.c. 

7.  200  c.c.  Erlenmeyer  flask. 

8.  A  2  c.c.  pipette. 

9.  Nessler's  reagent. 

10.  Standard  solution  of  Ammonia  (i   c.c.  =  o-oi  milligram  of 

NH3). 

Before  beginning  the  process  for  the  estimation  of  ammonia  it 
is  advisable  to  practise  the  method  first  on  known  quantities 
of  ammonia  added  to  water,  and  secondly  on  unknown  quantities 
which  are  also  added  to  the  water. 


14  WATER   ANALYSIS 

1.  In  order  to  do  this  add  i  c.c,  2,  3,  etc.,  up  to  10  and  15  c.c. 

of  the  standard  ammonia  solution  to  each  of  ten  of  the 
Nessler  glasses,  fill  each  up  to  the  50  c.c.  mark  with  distilled 
ammonia-free  water,  and  add  2  c.c.  of  Nessler's  solution. 
Allow  this  to  stand  for  two  minutes  after  well  shaking. 

2.  Compare  these  tints  carefully  in  order  to  get  an  idea  of  the 

depth  of  tint  produced  by  the  varying  quantities  of  ammonia. 
After  having  become  familiar  with  these  tints,  add  a  small 
unknown  quantity  of  ammonia  to  the  50  c.c.  of  distilled 
water  in  a  Nessler  glass  and  estimate  the  amount  added. 

3.  Repeat  this  several   times  in    order  to  get    an    idea    of  the 

approximate  amount  of  ammonia  which  a  certain  tint 
indicates. 

Suppose  that  we  find  that  5  c.c.  of  the  standard  ammonia 
solution  gives  a  darker  tint  than  the  unknown  quantity,  we 
add  3  c.c.  and  find  this  too  little  ;  next  we  add  4  c.c.  and 
also  find  this  too  Httle ;  the  addition  of  4*5  exactly  matches, 
that  is  to  say,  our  unknown  quantity  contains  the  equivalent 
of  4*5  c.c.  of  the  standard  ammonia  solution.  As  the  standard 
ammonia  contains  o'oi  milligram  per  c.c.  it  is  evident  that 
the  50  c.c.  of  water  contains  4*5  x  •oi:=o-45  milligrams.  There 
is  another  method  of  determining  the  amount  present  in  a 
Nessler  glass  when  the  tint  cannot  be  exactly  matched  by 
any  of  the  standard  solutions  we  have  made.  For  example, 
the  unknown  quantity  is  found  to  be  less  than  the  equivalent 
of  5  c.c.  of  the  standard  ammonia.  By  means  of  a  clean 
pipette  remove  some  of  the  fluid  in  the  standard  solution  until, 
when  both  glasses  are  looked  at  from  above  over  the  white  slab, 
the  tints  are  exactly  alike  ;  next  measure  the  fluids  left.  Suppose 
35  c.c.  are  left  of  the  standard  solution,  and  match  50  c.c.  of  the 
test  solution  ;  then  the  ammonia  in  the  test-glass  equals  ?^  of 
the  standard.  But  the  standard  contains  5  c.c.  of  the  ammonia 
solution;  therefore  the  test-glass  contains  ^^^  of  0*05  milligrams 
of  NH3,  and  this  equals  0*035  milligrams  of  ammonia. 

If  the  fluid  contained  in  the  test-glass  is  deeper  than  that  in 
the  standard  glass  with  the  5  c.c.  of  the  ammonia  solution,  some 
of  the  fluid  from  the  test-glass  must  now  be  removed  until  the 
tints  are  exactly  alike.  Suppose  10  c.c.  have  to  be  removed, 
then  40  of  the  test  equal  50  of  the  standard  ;  therefore  50  of  the 
sample  equal  |{}  of  50  c.c.  of  the  standard.  But  the  standard 
contains  0*05  milligrams  of  ammonia;  therefore  our  test  contains 
0-0625  milligrams  of  ammonia. 


FREE   AMMONIA  15 

The  Process 

1.  Rinse  out  the  retort  or  flask  with  strong  HCl,  and  subsequently 

with  good  tap  water,  until  all  traces  of  the  acid  have  disap- 
peared, then  rinse  out  well  with  two  or  three  lots  of  distilled 
ammonia-free  water  and  empty. 

2.  Fix  the  retort  or  flask  in  a  good  clamp  and  attach 'the  con- 

denser, which  is  also  supported  by  a  clamp. 

3.  When  the  retort  and  condenser  are  fitted  together,  connect 

the  outside  case  of  the  condenser  with  the  water  tap,  re- 
membering to  connect  it  in  such  a  way  that  the  water  runs 
in  from  below  upwards.     Do  not  turn  on  the  tap  yet. 

4.  Pour  about  500  c.c.  of  ammonia-free  distilled  water  into  the 

flask  or  retort,  add  a  few  grains  of  pure  sodium  carbonate 
and  a  few  pieces  of  broken  pumice.  The  latter  will  prevent 
*'  bumping."  Light  the  burner  and  put  it  under  the  flask, 
the  bottom  of  which  should  be  protected  with  wire  gauze. 

5.  Distil  until  the  steam  has  issued  from  the  lower  end  of  the 

condenser  for  several  minutes,  and  then  turn  on  the  water 
through  the  outer  casing  of  the  condenser. 

6.  Collect  about  2ooc.c.ofthewater,andaseach  50  c.c.  comes  over 

add  2  c.c.  of  Nessler.  If  the  condenser  and  retort  are  perfectly 
clean  there  will  be  no  colour  in  the  third  or  fourth  distillates. 

7.  After  thus  cleaning  the  condenser  and  flask,  add  500  c.c.  of 

the  water  to  be  examined.  The  small  amount  of  Na2C03 
present  in  the  flask  will  neutralize  any  acid  in  the  sample 
water,  and  leave  the  ammonia  free  to  be  distilled  off.  Re- 
place the  stopper  or  cork  and  begin  to  distil. 

8.  Distil  over  50  c.c.  into  a  Nessler  glass.     When  this  is  done 

collect  the  next  distillate  in  a  fresh  Nessler  glass  and  add 
2  c.c.  of  Nessler  to  the  first  distillate.  If  a  colour  is 
developed  upon  the  addition  of  the  Nessler,  determine  the 
amount  of  ammonia  present  as  explained  above.  When 
the  second  Nessler  glass  is  full  remove  that  and  place  the 
third.  Add  2  c.c.  of  Nessler  to  the  second  distillate  and  if 
there  is  still  a  colour  produced  determine  the  amount  of 
ammonia  in  the  second  distillate.  Continue  to  do  this  until 
the  addition  of  Nessler  to  the  distillate  produces  no  colour. 
(It  is  generally  found  that  the  whole  of  the  saline  ammonia 
comes  ofl"  in  the  first  150  c.c.  of  the  distillate,  so  that  one 
always  expects  to  find  no  ammonia  in  the  fourth  50  c.c. 
distilled  over.) 


i6  WATER   ANALYSIS 

9.  Having  determined  the  quantity  of  ammonia  present  in  each 
of  the  distillates,  add  these  quantities  together  and  it  will 
represent  the  quantity  of  saline  ammonia  present  in  500  c.c. 
of  the  water.  From  this  the  amount  present  can  be  readily 
expressed  in  parts  per  100,000. 

EXAMPLE 

The  first  distillate  of  50  c.c.  was  matched  by  i"5  c.c.  of 
standard  NH3. 

The  second  distillate  of  50  c.c.  was  matched  by  I'o  c.c.  of 
standard  NH3. 

The  third  distillate  of  50  c.c.  was  matched  by  0*5  c.c.  of 
standard  NH3. 

The  fourth  distillate  gave  no  colour  with  Nessler's  solution. 
.*.   the  three  distillates,  or  all  the  free  and  saline  ammonia  in  the 
500  c.c,  were  matched  by  3  c.c.  of  the  standard  NH3  solution. 

In  other  words,  500  c.c.  contained  o"o3  milligrams  of  ammonia. 
.*.  100      „  „         o-oo6         „        „  ^       „ 

Or  there  were  *oo6  parts  of  free  and  saline  ammonia  in  100,000 
parts  of  the  sample. 

ALBUMINOID   AMMONIA 

The  Process 

1.  While  the  saline  ammonia  is  being  distilled  off,  50  c.c.  of  the 

alkaline  permanganate  solution  should  be  poured  into  an 
Erlenmeyer  flask  and  about  150  c.c.  of  ammonia-free  water 
added.  This  must  now  be  boiled  until  the  bulk  is  reduced 
to  100  c.c. 

2.  When  all  the  free  and  saline  ammonia  has  been  distilled  off 

and  the  distillation  stopped,  the  alkaline  permanganate  is 
poured  carefully  into  the  flask  or  retort,  the  stopper  is  re- 
placed, and  the  distillation  begun  again. 

3.  As  the  water  comes  off  it  should  be  collected  in  the  Nessler 

glasses  as  before,  and  the  Nessler  reagent  added. 

4.  The  quantity  of  ammonia  must  be  estimated  as  in  the  case  of 

the  saline  ammonia. 

Explanation 

The  nitrogenous  matter  in  the  water  is  reduced  by  boiling  with 
alkaline  permanganate,  and  converted  into  ammonia,  which  is 
distilled  off. 


TESTS    FOR   NITRITES  17 

Notes 

The  preliminary  boiling  of  the  permanganate  ensures  the 
absence  of  both  ammonia  and  organic  matter,  and  therefore  all 
the  ammonia  distilled  over  must  come  from  the  water  under 
examination. 

The  organic  matter  is  not  all  reduced  instantaneously,  but  more 
or  less  gradually.  The  ammonia  does  not  therefore  come  off 
necessarily  in  the  first  150  c.c.  of  the  distillate  as  does  the  saline 
ammonia. 

Every  50  c.c.  of  water  as  it  comes  off  must  therefore  be  tested 
with  Nessler  reagent  until  there  is  no  reaction. 

If  a  sample  of  water  contains  a  considerable  quantity  of 
organic  matter,  it  sometimes  happens  that  there  is  a  danger  of 
the  retort  boiling  almost  dry.  When  this  occurs  100  or  200  c.c. 
of  organically  pure  ammonia-free  water  must  be  added  to  the 
retort,  and  the  distillation  continued. 


TESTS   FOR  THE  PRESENCE  OF  NITRITES 
BY  POTASSIUM  IODIDE  AND  STARCH 

Apparatus,  etc.,  required 

1.  Two  Nessler  glasses. 

2.  Potassium  iodide  solution. 

3.  Starch  solution. 

4.  Dilute  sulphuric  acid  (about  10%). 

1.  Pour  50  c.c.  of  the  water  to  be  tested  in  a  Nessler  glass  and 

50  c.c.  of  distilled  water  into  another. 

2.  Add  a  few  drops  of  the  KI  solution  to  each  of  the  Nessler 

glasses  and  then  a  few  drops  of  the  starch  solution. 

3.  Add  a  few  drops  of  dilute  sulphuric  acid  to  each  tube. 

If  nitrites  are  present,  a  blue  colour  will  be  immediately 
formed,  the  depth  of  the  colour  depending  on  the  amount  of 
nitrites  present. 

Explanation 

The  sulphuric  acid  liberates  nitrous  acid  from  the  nitrites. 
The  free  nitrous  acid  then  liberates  iodine  from  the  potassium 
iodide,  and  this  iodine  combines  with  the  starch  and  gives  the 
blue  colour  (W^- 

This  is  an  extremely  easy  method  of  determining  the  presence 


i8  WATER   ANALYSIS 

of  nitrites,  but  care  must  be  taken  to  make  the  observations  at 
once,  since  nitrates  may  give  the  same  reaction  after  the  lapse  of 
a  short  interval. 

BY  METAPHENYLENE-DIAMINE-HYDROCHLORIDE 

GRIESS'S   METHOD 

Apparatus    required 

1.  Two  Nessler  glasses. 

2.  Solution  of  metaphenylene-diamine-hydrochloride. 

1.  Pour  50  c.c.  of  the  water  to  be  tested  into  a  Nessler  glass,  and 

50  c.c.  of  distilled  water  into  another. 

2.  Add  to  each  glass   i  c.c.  of  the  solution  of  metaphenylene- 

diamine-hydrochloride,  and  a    few    drops    of  hydrochloric 
acid. 

If  nitrites  are  present  a  brown  colour  will  be  formed  in  the 
sample,  due  to  the  production  of  Bismarck  Brown. 

Explanation 

Metaphenylene-diamine-hydrochloride  is  a  colourless  solution 
which  in  the  presence  of  nitrous  acid  gives  rise  to  triamido-azo- 
benzol  or  Bismarck  Brown,  and  hence  colours  the  solution.  The 
hydrochloric  acid  is  added  to  liberate  nitrous  acid  from  the 
Nitrites  present  in  the  water. 

2C6H,(NHo)2-  HCl  +  HNO2- 

CgHVNHg-N  :  N-C6H3(NH2)2 '  HCl  +  2H2O 

Notes 

Metaphenylene-diamine-hydrochloride,  when  dissolved  in  water, 
tends  to  become  dark  in  colour,  and  this  interferes  with  the 
delicacy  of  the  test.  The  solution  is  better  when  made  fresh ; 
failing  this  it  must  be  filtered  through  animal  charcoal  until  it  is 
colourless. 

QUANTITATIVE   ESTIMATION   OF   NITRITES 
GRIESS'S    METHOD 

Apparatus  required 

1.  Nessler  glasses. 

2.  Solution  of  metaphenylene-diamine-hydrochloride. 

3.  Standard  nitrite  solution. 


TESTS    FOR    NITRATES  19 

The  Process 

1.  Into  each  of  ten  Nessler  glasses  put  varying  amounts  of  the 

standard  nitrite  solution — i  c.c,  2  c.c,  etc.,  to  10  c.c. 

2.  Fill  each  glass  up  to  the  50  c.c.  mark  with  distilled  water. 

Add  to  each  a  few  drops  of  HCl. 

3.  Add  50  c.c.  of  the  sample  water  to  another  Nessler  glass, 

together  with  a  few  drops  of  HCl. 

4.  Add  I  c.c.  of  metaphenylene  diamine-hydrochloride  solution 

to  each  glass. 

5.  Compare   the  various  tints,  and  see  with  which  of  the  ten 

glasses  the  sample  water  matches. 

6.  If  the  sample  is  too  dark,  dilute  with  twice  or  more  times  the 

volume  of  distilled  water  and  repeat  the  process  from  the 
beginning. 

EXAMPLE 

It  was  found  that  the  Nessler  glass  containing  the  sample 
water  matched  the  Nessler  glass  in  which  there  were  5  c.c.  of 
the  standard  nitrite  solution. 

Now  I  c.c.  of  the  standard  nitrite  solution  =  o*oi  milligrams 
of  N2  as  nitrite. 

.*.  5  c.c.  of  the  standard  nitrite  solution  =  0*05  milligrams 
of  N2  as  nitrite. 

Thus  in  50  c.c.  of  the  water  under  examination  there  were 
0*05  milligrams  of  Ng  as  nitrite. 

So  in  100  c.c.  there  were  o'l  milligrams  of  Ng  as  nitrite,  or, 
in  other  words,  o'l  part  per  100,000. 

Notes 

Griess's  method  estimates  nitrites  alone. 

The  principle  involved  is  the  same  as  in  Nessler's  method  of 
estimating  ammonia,  and  the  student  will  find  that  when  he  has 
mastered  the  one  method  the  other  will  come  easily  to  him. 

TESTS   FOR  THE  PRESENCE  OF   NITRATES 

BRUCINE   METHOD 

1.  2  c.c.  of  the  suspected  water  are  placed  in  a  perfectly  clean 

white  porcelain  dish  and  evaporated  to  dryness. 

2.  A  drop  of  pure  H.^SO^  is  allowed  to  drop  on  the  residue. 

3.  A  minute  crystal  of  Brucine  is  now  added. 


20  WATER   ANALYSIS 

If  nitrates  are  present,  a  pink  colour  will  appear.  This  test 
is  an  extremely  delicate  one,  a  reaction  being  obtained  when  the 
nitrate  is  present  in  the  proportion  of  only  i  in  10,000,000. 


DIPHENYLAMINE  TEST 

A  few  crystals  of  diphenylamine  are  put  into  a  porcelain  dish. 

I  c.c.  of  pure  HoSO^  is  added. 

A  little  of  the  suspected  water  is  poured  into  the  dish.     If 

nitrates   are  present  a  blue   colour  will  appear.     Nitrites 

give  no  colour  with  this  test. 


BY   POTASSIUM   IODIDE  AND   STARCH 

The  method  is  the  same  as  in  testing  for  nitrites,  and  is  of  no 
use  for  detecting  the  presence  of  nitrates  if  the  nitrites  are  also 
there.  If,  however,  no  colour  comes  at  once,  but  does  come 
after  the  lapse  of  a  few  minutes,  it  may  be  inferred  that  nitrates, 
and  not  nitrites,  are  present  in  the  water.  The  test,  however,  is 
not  so  satisfactory  as  those  already  mentioned. 


QUANTITATIVE   ESTIMATION   OF   NITRATES 
PHENOL-SULPHONIC  ACID  METHOD 

Apparatus,  etc.,  required 

1.  Evaporating  dishes. 

2.  Nessler  glasses. 

3.  Phenol-sulphonic  acid  solution. 

4.  Standard  nitrate  solution. 

The  Process 

1.  Place  10  c.c.  of  water  in  the  dish  and  evaporate  to  dryness  on 

the  water  bath. 

2.  Place  in  another  dish  i  c.c.  of  the  standard  nitrate  solution 

and  evaporate  to  dryness  in  the  same  manner. 

3.  To  each  of  the  dried  residues  add  i  c.c.  of  phenol-sulphonic 

acid,   I   c.c.   of  distilled  water,   and   2   or  3  drops  of  sul- 
phuric acid. 

4.  Warm  gently  over  the  water  bath. 

5.  Distilled  water  is  now  added  and  excess  of  ammonia,  and  the 

bulk  of  each  is  made  up  to  100  c.c. 


NITRATES    AND    NITRITES  21 

6.  50  c.c.  of  the  solutions  are  pipetted  into  two  Nessler  glasses. 

7.  Compare  the  tints  and  pipette  off  from  the  darker  tinted  glass 

as  much  of  the  water  as  is  necessary  to  make  the  tints  alike 
when  viewed  from  above. 

8.  Calculate  from  the  quantities  remaining  in  the  glasses  the 

amount  of  nitrate  present. 

Explanation 

The  nitrates  present  in  the  water  convert  the  phenol-sulphonic 
acid  into  a  mixture  of  nitro  compounds,  the  chief  of  which  is 
trinitrophenol,  the  ammonium  salts  of  which  are  coloured. 

C,H,(0H)S03H  +  3HN03  =  C6H2(OHXN02)3  +  H2S04+2H20 

The  depth  of  the  colour  is  then  a  measure  of  the  amount  of 
these  compounds  present,  and  so  of  the  nitrates  originally  present 
in  the  water. 

Notes 

The  phenol-sulphonic  acid  method  estimates  nitrates  alone. 
It  cannot  be  used  for  the  estimation  of  nitrates  if  the  water  under 
examination  contains  much  organic  matter  (as,  for  example,  does 
a  sewage  effluent),  because  such  organic  matter  gives  much 
charring  when  the  water  is  evaporated,  and  so  interferes  with 
the  colour  of  the  trinitrophenol.  In  such  a  case  one  of  the 
following  methods  which  estimate  both  nitrites  and  nitrates  must 
be  employed,  and  when  the  result  is  obtained  the  nitrate  value 
of  the  water  is  determined  by  subtracting  from  the  result  the 
figure  for  nitrites  obtained  by  Griess's  method,  the  remainder, 
of  course,  being  the  amount  of  nitrates  present. 

QUANTITATIVE   ESTIMATION   OF   NITRITES 
AND   NITRATES 

I.     INDIGO     METHOD 

Apparatus,  etc.,  required 

1.  A  small  beaker  holding  about  60  c.c. 

2.  A  small  glass  stirring  rod. 

3.  A  20  c.c.  pipette. 

4.  A  graduated  glass  cylinder  to  hold  20  c.c. 

5.  A  burette  graduated  in  o"i  c.c. 

6.  Pure  redistilled  nitrate-free  concentrated  sulphuric  acid. 

7.  Standard  indigo  solution. 


22  WATER   ANALYSIS 

The  Process 

1.  Fill  the  burette  with  the  standard  indigo,  and  make  a  note  of 

the  height  of  the  indigo,  reading  the  top  of  the  meniscus. 

2.  Pipette  20  c.c.  of  the  water  into  the  beaker,  taking  care  to 

drain  the  pipette. 

3.  Measure  20  c.c.  of  H2SO4  in  the  cylinder. 

4.  Pour  the  H2SO4  into  the  beaker,  stirring  briskly,  and  do  not 

wait  for  the  last  drops  of  the  acid  to  drain. 

5.  At  once  allow  the  indigo  to  run  into  the  now  hot  mixture  drop 

by  drop,  until  the  greenish  evanescent  colour  becomes  per- 
manent. 

6.  Read  off  the  height  of  the  indigo  in  the  burette. 

The  estimation  must  now  be  repeated,  in  a  slightly  different 
order,  as  follows: — 

1.  Pipette  the  20  c.c.  of  water  into  the  beaker. 

2.  Allow  about  0*5  c.c.  less  of  the  indigo  than  was  required  in 

the  first  estimation  to  run  into  the  beaker. 

3.  Now  pour  in  the  HoSO^,  and  stir  briskly. 

4.  Immediately  the  colour  is  discharged,  add  more  indigo  drop 

by  drop,  until  the  colour  is  once  more  permanent. 

5.  Now  read  off  the  height  of  the  indigo. 

Explanation 

The  concentrated  HgSO^  decomposes  the  nitrites  and  nitrates 
present  and  liberates  free  nitric  acid.  This  then  oxidizes  the 
indigo,  forming  isatin,  which  is  colourless.  Directly  all  the 
nitric  acid  has  been  used  up  a  further  addition  of  indigo  will  not 
be  oxidized  and  will  therefore  retain  its  colour.  The  amount  of 
indigo  required  to  give  a  permanent  colour  will  indicate  the 
quantity  of  nitrates  and  nitrites  present  in  the  20  c.c.  of  water. 

EXAMPLE 

A  second  or  control  estimation  gave  the  following  : — 

I  St  reading  of  burette  .  .  .     io'3  c.c. 

2nd     „  „  ...     12-5    „ 

Amount  of  indigo  used  .  .  .2*2    „ 

I   c.c.  of  indigo  =  o*o86  milligrams  of  Ng 
.-.  2-2  c.c.    „       =0-1936         „  „ 


NITRATES    AND    NITRITES  23 

But  this  amount  was  contained  in  20  ex.  of  the  water. 
.'.  in  100  CO.  there  will  be  0*968  milligrams  of  Ng 
or  0*968  parts  per  100,000  of  the  water. 

Notes 

It  is  common  practice  to  standardize  the  indigo  for  the  amount 
of  water  that  is  to  be  used.  The  same  quantity  should  therefore 
always  be  used.     20  c.c.  has  been  found  to  be  convenient. 

If  the  nitrates  are  present  in  considerable  amount,  the  solution 
becomes  so  dark  that  it  is  very  difficult  to  determine  the  "  end 
point "  with  accuracy.  In  these  cases  it  becomes  necessary  to 
dilute  the  water,  generally  from  i  to  4  times.  Very  occasionally 
it  becomes  necessary  to  dilute  10  or  even  20  times.  If  it  is 
necessary  to  dilute  4  times,  10  c.c.  should  be  thoroughly  well 
mixed  with  30  c.c.  of  distilled  water,  and  20  c.c.  of  the  diluted 
water  pipetted  into  the  beaker  and  treated  as  in  the  case  of  the 
undiluted  water. 

When  20  c.c.  of  the  concentrated  H2SO4  are  added,  the  right 
amount  of  heat  is  generated  to  allow  the  oxidation  of  the  indigo 
by  the  liberated  nitric  acid.  The  estimation  must  therefore  be 
done  as  quickly  as  possible.  It  is  in  order  that  this  temperature 
may  be  maintained  up  to  the  end  point  that  the  second  order  of 
procedure  given  above  is  adopted. 

II.     COPPER-ZINC    COUPLE    METHOD 

Apparatus,  etc.,  required 

1.  Zinc  foil,  about  9  sq.  inches. 

2.  3%  solution  of  CUSO4. 

3.  Wide-mouthed,  glass-stoppered  bottle  of  about  8  oz.  capacity. 

4.  100  c.c.  graduated  measuring-glass. 

5.  10  c.c.  pipette. 

6.  Apparatus  as  in  the  estimation  of  free  and  saline  ammonia. 

The  Process 

1.  Immerse  the  zinc  foil  in  the  copper  sulphate  solution  until  the 

surface  of  the  zinc  is  coated  with  metallic  copper. 

2.  Wash  the  foil  in  ammonia- free  water. 

3.  Place  the  foil  in  the  glass-stoppered  bottle. 

4.  Put  about  120  c.c.  of  the  water  to  be  examined  into  the  bottle. 

5.  Stopper  tightly,  and  put  the  bottle  away  in  a  warm  dark  place 

until  the  following  day. 


24  WATER    ANALYSIS 

6.  Then  remove  lo  c.c.  of  the  water  and  test  for  the  presence  of 

nitrites  by  Griess's  method. 

7.  If  nitrites  are  present,  restopper  the  bottle,  put  it  away  again 

for  12  hours  and  then  test  again. 

8.  If  nitrites  are  absent,   measure  out    100  c.c.    of  the   water, 

transfer  it  to  a  flask  or  retort,  and  estimate  the  ammonia  in 
the  ordinary  way. 

From  the  amount  of  ammonia  obtained,  the  nitrogen  as  nitrites 
and  nitrates  is  readily  calculated. 

It  will  be  evident  that  by  this  process  any  ammonia  which  is 
present  in  the  water  originally,  will  be  present  after  the  conversion 
of  the  nitrates  and  nitrites  into  ammonia,  and  therefore  the 
ammonia  found  will  represent  the  ammonia  reduced  from  the 
nitrates  plus  the  original  ammonia.  The  amount  of  original 
ammonia  must  be  deducted  in  order  to  find  the  true  amount  of 
nitrates  and  nitrites. 

Explanation 
The  zinc  copper  couple  liberates  nascent  hydrogen  from  the 
water,  and  this  reduces  the  nitrates  and  nitrites  to  ammonia. 
HNO3  +  8H  -  NH3  +  3H.O 
HN02+6H  =  NH3+2H20 


OXYGEN   ABSORBED 

TIDY'S   PROCESS 

Apparatus,  etc.,  required 

1.  Two  glass-stoppered  bottles  holding  about  350  c.c. 

2.  A  water  bath  or  incubator  regulated  at  27°  C. 

3.  A  50  c.c.  burette  graduated  in  tenths  of  a  c.c. 

4.  Organically  pure  ammonia-free  water. 

5.  Thiosulphate  solution. 

6.  Starch  solution. 

7.  Potassium  iodide  solution. 

8.  25%  sulphuric  acid. 

9.  Standard  permanganate  solution. 

The  Process 

I.  Measure  250  c.c.  of  good  distilled  water  into  one  bottle  (the 
control),  and  250  c.c.  of  the  water  under  examination  into 
the  other. 


TIDY'S    PROCESS  25 

2.  Into  each  of  these  measure  10  c.c.  of  the  standard  potassium 

permanganate  solution  and  10  c.c.  of  the  specially  prepared, 
organically  pure  25%  H0SO4. 

3.  Shake  the  bottles  up  and  place  in  the  water  bath  at  27°  C.  for 

four  hours. 

4.  At  the  end  of  this  time  add  a  few  drops  of  the  KI  solution 

to  each  bottle.  The  pink  colour  will  disappear  and  be 
replaced  by  a  yellow  one. 

5.  Fill  the  burette  with  thiosulphate  solution,  and  carefully  read 

the  height  of  the  fluid. 

6.  Run  the  thiosulphate  into  the  control  bottle  until  the  yellow 

colour  is  almost  discharged  and  then  add  a  few  drops  of 
starch  solution.  The  colour  will  now  turn  blue.  Add  the 
thiosulphate  cautiously  until  all  the  colour  is  discharged,  and 
read  off  the  height  of  the  fluid  in  the  burette. 

7.  Repeat  this  with  the  bottle  containing  the  sample  of  water. 

Explanation 

The  potassium  permanganate  in  the  presence  of  sulphuric  acid 
oxidizes  the  organic  matter  in  the  water. 

KgMnsOs  +  3H0SO4  -  K2SO4  +  2MnS04  +  3U.fi  +  5O 

The  amount  of  this  organic  matter  is  to  a  certain  extent  gauged 
by  the  quantity  of  permanganate  used  up. 

The  control  bottle,  containing  only  distilled  water  and  there- 
fore no  organic  matter,  will  use  up  no  oxygen,  and  so  will  contain 
permanganate  at  the  end  of  the  four  hours,  the  equivalent  of 
I  milligram  of  oxygen. 

The  potassium  iodide  is  decomposed  by  the  permanganate, 
and  iodine  is  liberated. 

KoMnoOg  +  SH.SO^-f  ioKI  =  6KoSO^+2MnSO^  +  8H20  +  5lo 

The  amount  of  iodine  liberated  will  be  in  proportion  to  the 
amount  of  permanganate  in  solution  (i.e.  not  used  up).  In  this 
case  it  will  be  the  equivalent  of  i  milligram  of  oxygen. 

The  amount    of  iodine    liberated    is    now   measured    by   the 
quantity  of  thiosulphate  required   to  decolourize   the  solution, 
which  it  does  according  to  the  following  equation : — 
2  NaoSoOs  +  h  =  2NaI  +  NaoS^O^ 

The  starch  solution  is  added  towards  the  end  of  the  operation 
in  order  the  more  easily  to  determine  the  actual  end  point.  It 
performs  no  other  function. 


26  WATER   ANALYSIS 


EXAMPLE 

Control  (C)  took  15*2  c.c.  of  the  thiosulphate  to  decolourize 
the  iodine. 

The  sample  of  water  took  13*4  c.c.  to  decolourize  it. 

1 5 "2  c.c.  of  thiosulphate  therefore  represent  10  c.c.  of  the  per- 
manganate solution,  and  this  equals  i  milligram  of  available 
oxygen. 

The  sample  of  water  required  i3"4  c.c.  The  difference  be- 
tween this  and  15  "2  c.c.  represents  the  amount  of  oxygen  absorbed 
by  the  water.     This  difference  is  i'8  c.c. 

Now  as    1 5 "2    c.c.   of  thiosulphate  =  I    milligram   of  oxygen, 

1-8 
I  "8  c.c.  will  be  — :— of  i    milligram,  which  equals  o*ii8  milli- 
grams. 

But  250  c.c.  of  the  water  was  taken;  therefore  100  c.c.  will 
absorb  0*047  milligrams;  or,  in  other  words,  the  oxygen 
absorbed  during  four  hours  at  27°  C.  is  equal  to  0*047  parts  per 
100,000. 

Notes 

The  results  obtained  by  this  method  merely  give  an  indication 
as  to  whether  or  not  there  is  much  oxidizable  organic  matter  in 
the  water.  Various  analysts  take  various  times  and  temperatures 
in  performing  this  experiment.  For  examination  purposes  the 
student  will  find  that  three  hours  at  room  temperature  will  be 
the  most  convenient  conditions  under  which  to  perform  the 
experiment. 

One  of  the  chief  reasons  for  making  a  control  examination  for 
each  sample  tested,  is  that  the  solution  of  thiosulphate  undergoes 
changes  and  gradually  becomes  weaker.  The  trouble  of  con- 
stantly having  a  standard  solution,  therefore,  would  be  found  in 
practice  far  greater  than  making  a  control  each  time.  The 
purpose  in  allowing  the  control  to  stand  along  with  the  sample 
is  to  eliminate  the  possibilities  of  error  due  to  the  destruction 
of  the  permanganate  by  any  condition  other  than  the  organic 
matter  present  in  the  sample. 

If,  as  sometimes  happens  with  a  bad  water  such  as  sewage,  the 
10  c.c.  of  permanganate  is  totally  decolourized  before  the  expiry 
of  the  four  hours,  a  further  10  c.c.  should  be  added,  and  if 
necessary  a  third  10  c.c,  and  the  amount  of  thiosulphate  used 
to  decolourize  the  iodine  liberated  deducted  from  twice  or  three 


POISONOUS    METALS  27 

times  that  required  to  decolourize  the  control,  in  order  to  obtain 
the  equivalent  of  oxygen  absorbed,  in  terms  of  thiosulphate. 

This  method  of  ascertaining  the  amount  of  organic  matter 
present  in  a  sample  of  water  is  useless  in  the  presence  of  iron 
in  the  ferrous  state,  since  this  takes  up  the  permanganate  with 
great  avidity. 

POISONOUS   METALS 

A.  LEAD 

I.  Qualitative  Tests 

a.    IVi'/k  Sulphuretted  Hydrogeji 

Pipette  about  100  c.c.  of  the  water  into  a  Nessler  glass,  add 
two  or  three  drops  of  acetic  acid,  and  then  several  drops  of 
a  saturated  aqueous  solution  of  HgS.  Stir  the  mixture  well.  If 
there  is  an  appreciable  amount  of  lead  in  the  water,  there  will  be 
a  brown  colour  developed  directly. 

b.    With  Fotasshwi  Chromate 

If  the  HoS  gives  a  decided  colour  with  the  sample  of  water, 
add  a  few  drops  of  KCrO^  to  a  fresh  100  c.c.  If  lead  is  present, 
a  yellow  precipitate  will  be  formed. 

If  only  a  very  faint  darkening  is  observed  with  the  HgS  it  is 
necessary  to  concentrate  the  water.  This  is  done  by  evaporating 
about  250  c.c.  in  an  evaporating  dish  to  20  c.c.  and  then  adding 
the  KCrO^.  By  this  means  the  precipitate  is  much  more  easily 
seen. 

c.    With  Sulphuric  Acid 

Add  a  few  drops  of  HgSO^  to  100  c.c.  of  the  water  and  allow 
it  to  stand  for  some  time.  A  white  precipitate  of  lead  sulphate 
will  be  formed. 

2.  Quantitative  Estimation 

Having  now  determined  that  lead  is  present  in  the  water,  it 
remains  to  find  the  quantity. 

1.  Measure  100  c.c.  of  the  water  into  a  Nessler  glass,  add  a  few 

drops   of  acetic    acid   and    several   drops    of  sulphuretted 
hydrogen. 

2.  Run  100  c.c.  of  distilled  water  into  another  Nessler  glass,  add 

a  few  drops  of  acetic  acid   and   several   of  sulphuretted 
hydrogen. 


28  WATER    ANALYSIS 

3.  Allow   the  standard  solution  of  lead  (i   c.c.  =  o'i    milligram 

of  Pb)  to  run  into  this,  drop  by  drop,  stirring  constantly 
until  the  depth  of  colour  is  the  same  in  both  glasses. 

4.  Read  off  the  quantity  of  lead  solution  used,  and  calculate  the 

quantity  of  lead  in  the  sample. 

EXAMPLE 

100  c.c.  of  the  water  were  found  to  contain  as  much  lead  as 
was  present  in  2  c.c.  of  the  standard  lead  solution. 

I  c.c.  =  o'i  milligrams  of  lead    ,'.2  c.c.  =  0*2  milligrams  of  lead 
But  this  was  present  in   100  c.c,  i.e.  there  are  o"2  parts  of 
lead  in  100,000  of  the  water. 

Notes 

If  a  very  small  quantity  of  lead  is  i)resent  in  the  water,  and  it 
is  necessary  to  know  the  exact  amount,  250  or  500  c.c.  of  the 
water  acidified  with  acetic  acid  should  be  evaporated  almost  to 
dryness.  The  residue  should  be  poured  on  to  a  small  filter- 
paper,  and  the  dish  and  filter-paper  washed  well  with  small 
quantities  of  distilled  water  acidified  with  acetic  acid.  The 
washing  should  be  collected  in  a  Nessler  glass  and  made  up 
to  50  c.c. 

The  determination  is  now  proceeded  with,  and  the  quantity 
found  will  be  that  present  in  250  c.c.  of  the  original  water. 

If  copper  is  present  as  well  as  lead,  the  above  method  will 
estimate  both  these  metals.  The  copper  must  be  estimated 
separately,  as  will  be  seen  later,  and  the  amount  thus  obtained 
deducted  from  that  obtained  by  the  H^S  method. 

The  difference  will  be  the  quantity  of  lead. 

B.     COPPER 

I.  Qualitative  Tests 

a.  With  Sulphuretted  Hydrogen 

This  test  is  performed  in  exactly  the  same  manner  as  was 
described  under  lead. 

b.  With  Potassium  Fer?-ocya?iide 

I.  Place  about    100   c.c.   of  the  water   in  a  Nessler  glass  and 
acidulate  with  a  little  dilute  hydrochloric  acid. 


POISONOUS    METALS  29 

2.  Add  a  few  drops  of  potassium  ferrocyanide  and  stir  up  well. 
A  brown  or  chocolate  colour  will  be  developed  if  copper  is 
present,  owing  to  the  formation  of  copper  ferrocyanide. 

c.  By  the  Platinum- Steel  Couple 

This  is  an  extremely  delicate  test,  and  is  very  simple. 

Half  fill  a  platinum  dish  with  the  water  and  acidulate  with 
HCl.  Then  lay  a  large  polished  steel  needle  in  the  dish  so  that 
one  end  rests  on  the  bottom,  and  the  other  on  the  edge.  Part 
will  thus  be  immersed  and  part  dry.  After  being  in  this  position 
for  about  half  an  hour  the  needle  is  withdrawn  and  examined. 
If  copper  is  present  in  the  water  there  will  be  a  deposit  on  the 
needle.  This  deposit  can  be  made  more  conspicuous,  if  neces- 
sary, by  allowing  it  to  come  in  contact  with  bromine  vapour  for  a 
few  seconds. 

2.  Quantitative  Estimation 

Having  determined  that  copper  is  present,  it  remains  to 
estimate  the  amount. 

1.  Measure  100  c.c.  of  the  water  into  a  Nessler  glass,  add  a  few 

drops  of  dilute  HCl,  and  then  sufficient  K^FefCN)^  to 
produce  the  maximum  colour. 

2.  Measure  100  c.c.  of  distilled  water  into  another  Nessler  glass, 

add  the  same  quantities  of  HCl  and  K^FefCNjg  as  were 
added  to  the  sample. 

3.  Allow  the  standard  solution  of  copper  to  run  into  this  drop 

by  drop  until  the  colours  match.  When  this  occurs,  read  off 
the  quantity  used,  and  calculate  the  amount  of  copper  present 
per  100,000. 

Notes 
In  testing  for  copper,  controls  should  always  be  made  in  a 
similar  manner  to  those  described  for  the  determination  of  the 
presence  of  lead. 

C.     IRON 

I.  Qualitative  Tests 

a.  With  Ammo7iium  Sulphide 
Take  about  100  c.c.  of  the  water  in  a  Nessler  glass,  add  a  few^ 
drops  of  ammonia  solution  and  also  a  few  drops  of  solution  of 
ammonium  chloride.  Now  add  about  2  c.c.  of  a  solution  of 
ammonium  sulphide.  If  iron  is  present,  there  will  be  a  brown 
colour  developed. 


30  WATER   ANALYSIS 

b.    With  Potassium  Ferrocyanide  and  Ferricyanide 

To  loo  c.c.  of  the  water  add  a  few  drops  of  dilute  HCl  and 
a  few  drops  of  K_jFe(CN)Q  and  K3Fe(CN)g.  If  a  blue  colour 
develops,  iron  is  present  either  as  a  ferrous  or  a  ferric  salt. 

c.    With  Potassium  Siclphocyanide 

To  about  loo  c.c.  of  the  water  add  a  few  drops  of  pure 
dilute  HNO3  ^^<^  ^  crystal  of  KCNS.  If  iron  is  present  a  red 
colour  will  be  formed. 

2.  Quantitative  Estimation 

1.  Measure  100  c.c.  of  the  water  into  a  Nessler  glass,  and  add  a 

few  drops  of  nitric  acid  and  a  few  drops  of  a  solution  of 
potassium  ferrocyanide  until  the  blue  colour  produced 
reaches  the  maximum. 

2.  Measure  100  c.c.  of  distilled  water  into  another  Nessler  glass, 

add  a  few  drops  of  potassium  ferrocyanide  solution,  and 
then  add  the  standard  ferric  chloride  solution  until  the  blue 
colour  developed  matches  that  in  the  first  glass. 

3.  Measure  the  amount  of  standard  iron  solution  used,  and  thus 

calculate  the  amount  of  iron  present  in  the  sample  water. 

Another  method  is  to  use  potassium  sulphocyanide  instead  of 
the  ferrocyanide  as  an  indicator. 

D.    ZINC 

I.  Qualitative  Tests 

a.    With  Ammofiitwi  Sulphide 

Take  about  100  c.c.  of  the  water  in  a  Nessler  glass,  add  a  few 
drops  of  NH4HO,  and  also  a  few  drops  of  NH^Cl  solution.  Now 
add  about  2  c.c.  of  a  solution  of  fresh  (NH.JoS.  If  zinc  is 
present  in  any  but  the  minutest  traces,  a  white  precipitate  of  zinc 
sulphide  will  be  produced. 

b.    With  Potassium  Ferrocya7iide 

Acidulate  100  c.c.  of  the  water  with  a  few  drops  of  HCl  and 
add  a  few  drops  of  K^Fe(CN)^J.  If  zinc  is  present  in  any  but 
the  smallest  traces,  a  white  precipitate  will  be  formed. 

If   the  presence  of   zinc  is  suspected,  and  no  precipitate  is 


POISONOUS    METALS  31 

obtained  with  either  of  the  above  reagents,  half  a  htre  of  the 
water  should  be  evaporated  to  a  small  bulk  and  tested  in  the 
above  manner. 

2.  Quantitative  Estimation 

1.  Having  determined  that  neither  lead  nor  copper  is  present  in 

the  water,  measure  250  c.c.  into  an  evaporating  basin  and 
evaporate  over  the  water  bath  until  the  bulk  is  about  50  c.c. 

2.  Add  solution  of  NH^HO  and  filter  any  precipitated  hydrated 

oxide  of  iron.     To  the  filtrate  add  (NH^)oS  in  slight  excess. 

3.  Filter  the  water  through  an  ashless  filter-paper,  and  wash  the 

precipitate  with  dilute  (NH^)oS  solution. 

4.  Dry  the  precipitate  in  the  water  oven,   transfer  it  together 

with  the  filter-paper  to  a  tared  porcelain  crucible,  and  care- 
fully ignite  over  a  Buns  en  burner. 

5.  Allow  it  to  cool,  and  reweigh.     The  gain  in  weight  represents 

the  weight  of  oxide  of  zinc,  and  from  this  the  amount  of  zinc 
present  is  calculated. 

Notes  on  Poisonous  Metals  in  Drinking  Waters 

Copper  and  zinc  are  rarely  found  in  drinking  waters,  and 
when  they  are  present  they  are  derived  from  copper  and  zinc 
storage  vessels.  Iron  is  present  naturally  in  some  waters, 
especially  in  those  collected  from  the  greensand  strata.  Lead, 
the  metal  occurring  most  frequently  in  waters,  is  derived  from  the 
action  of  the  water  on  the  lead  pipes  through  which  the  supply 
is  distributed  to  the  consumers. 

The  kinds  of  water  which  have  a  marked  solvent  action  on 
lead  are : — 

1.  Soft  waters. 

2.  Waters  not  aerated. 

3.  Waters  containing  excess  of  nitrate. 

4.  Acid  waters  as  from  peaty  soils. 

From  the  hygienic  point  of  view,  the  presence  of  lead  in  water 
is  one  of  very  great  importance,  and  therefore  the  estimation  of 
the  lead  when  it  is  present,  or  even  the  detection  of  the  lead,  is  a 
very  important  point.  The  consumption  of  water  containing 
lead  gives  rise,  as  is  well  known,  to  symptoms  of  chronic  lead- 
poisoning,  and  it  is  laid  down  by  many  authorities  that  not  more 
than  -Qt^h.  grain  per  gallon  (0-025  parts  per  100,000)  should  ever 
be  present  in  a  water  intended  for  human  consumption.     Other 


32  WATER   ANALYSIS 

authorities  who  are  not  quite  so  rigid  lay  down  that  y^^-th  grain  is 
the  Hmit,  but  it  follows  from  what  has  been  said  above  that  when 
two  sources  of  water  are  available,  that  which  contains  no  lead, 
or  will  take  up  no  lead  from  the  pipes,  should  always  be  chosen 
in  preference  to  one  which  would  take  up  lead. 


GASES  IN  WATER 

The  detection  and  estimation  of  the  gases  contained  in  various 
samples  of  water  are  interesting,  but  are  of  questionable  hygienic 
import.  One  gas  is,  however,  of  some  importance,  namely 
oxygen,  and  a  brief  account  of  the  estimation  will  be  given. 
Should  the  reader  require  to  estimate  other  gases,  he  can  find  all 
the  details  in  several  text-books  more  pretentious  than  this. 


OXYGEN    IN  WATER 

WINKLER'S  METHOD 

Apparatus,   etc.,   required 

1.  Two  glass-stoppered  bottles  of  350  c.c.  capacity, 

2.  Solution  of  MnCl.2  (40  grammes  to  100  c.c). 

3.  Solution  of  K0H"'(33%)  and  KI  (10%)  in  water. 

4.  100  c.c.  burette,  graduated  in  o'l  c.c. 

5.  Freshly  prepared  starch  solution. 

6.  Sodium  thiosulphate  solution  (i  c.c.    =   0*25  milligrams  of 

oxygen). 

7.  Two  large  porcelain  dishes. 

8.  Pure  HoSO^. 

The  Process 

1.  Fill  one  of  the  bottles  with  distilled  water,  shaking  it  well  so 

that  as  much  oxygen  as  possible  shall  be  dissolved. 

2.  Fill  the  other  bottle  by  means  of  a  syphon  with  the  water 

under  examination.     Do  not  splash  the  water  or  shake 
the  bottle. 

3.  To    each    bottle    add    i    c.c.    of    the    strong    solution    of 

manganous  chloride. 

4.  To  each  bottle  add  2  c.c.  of  the  solution  containing  KOH 

and  KI. 

5.  Replace  the  stoppers,  taking  care  that  each  bottle  is  quite 

full  and  no  air  bubbles  are  included. 


DISSOLVED   OXYGEN  33 

6.  Invert  both  bottles  several  times,  so  as  to  mix  the  solutions 

in  them. 

7.  Put  the  bottles  away  in  a  dark  cupboard  for  fifteen  minutes. 

8.  Remove  the  bottles  from  the  cupboard,  and  pour  their  con- 

tents carefully,  and  without  splashing,  into  the  two  porce- 
lain dishes. 

9.  Label  the  dishes. 

10.  To  each  dish  add  3  c.c.  of  HoSO^.      The  brown  colour  that 

appears  is  due  to  free  iodine. 

11.  From  the  burette  run  into  the  dishes  enough  of  the  thiosul- 

phate  solution  to  discharge  the  brown  colour.  Use  the 
starch  solution,  as  in  Tidy's  process,  to  estimate  the  end 
point. 

12.  Read  the  burette,  and  note  the  amounts   of  thiosulphate 

solution  used  in  both  the  dishes. 

The  Explanation 

The  MnCU  with  the  KOH  forms  manganous  hydrate  : — 

"^  MnCl^  +  2KOH  -=  2KCI  +  Mn(0H)2 
And  when  this  Mn(OH)o  is  in  contact  with  water  containing 
dissolved  oxygen,   it  takes   up   the  oxygen   and  is    oxidized    to 
manganic  hydrate  : — 

4Mn(OH)o  +  2  HP  +  0.2  =  4Mn(OH)3 
The  amount  of  Mn(0H)3  formed  is  an  index,  therefore,  of  the 
amount  of  dissolved  oxygen  in  the  water. 

On  addition  of  H2SO4,  the  Mn(0H)3  is  converted  into 
manganic  sulphate,  which  latter  reacts  with  the  KI  and  liberates 
free  iodine. 

2Mn(OH)3  +  3H2SO4  =  Mn2(S0  J3  +  6H2O 
and  Mn2(S04)3  +  2KI  =  2MnS04+  K2S04  4-I2 
The  amount  of  iodine  liberated  is  proportionate  to  the  amount 
of  Mn2(S04)3,  and  so  proportionate  to  the  amount  of  Mn(0H)3, 
and  to  the  oxygen  dissolved  in  the  water. 

EXAMPLE 

The  dish  containing  the  distilled  water  shaken  with  air  was 
found  to  require  14*4  c.c.  of  sodium  thiosulphate  solution,  in 
order  that  the  colour  of  the  iodine  might  be  discharged. 
Now  I  c.c.  of  thiosulphate  solution  =  0-25  milligrams  of  oxygen 

.'.    i4'4         »  »  =3'6o  a  » 

.3 


34  WATER   ANALYSIS 

.*.   in  350  c.c.  of  distilled  water  there  were  3*6  milligrams  of 

oxygen 
.'.   in  100  c.c.  of  distilled  water  there  were  i'02  milligrams  of 

oxygen 
or  I '02  parts  of  oxygen  per  100,000  of  the  water. 

Again,  it  was  found  that  the  dish  containing  the  water  under 
examination  required  i2'6  c.c.  of  sodium  thiosulphate  solution, 
in  order  that  the  brown  colour  of  the  iodine  might  be  dis- 
charged. 

And  since   i   c.c.  of  thiosulphate  solution  =  0.2  5   milligrams  of 
oxygen 
.'.  i2"6  c.c.  of  thiosulphate  solution  =  3*15  milligrams  of  oxygen 
.*.  in  350  c.c.  of  the  sample  water  there  were  3*15  milligrams  of 

oxygen 
.*.  in  100  c  c.  of  the  sample  water  there  were  0*90  milligrams  of 
oxygen 
or  o*9  parts  of  oxygen  per  100,000  of  the  water. 

But  we  have  seen  that  a  fully  saturated  water  takes  up  i"o2 
parts  of  oxygen;  and  if  this  represents  100  per  cent,  then  the 
water  under  consideration  will  give  a  percentage  saturation  with 

r  0"9  X    100         „„        0/ 

oxygen  of  -^ =  88-2%. 

I'02  ^° 

The  result  may  be  returned  either  as  a  percentage  or  in  terms 
of  the  actual  amount  of  oxygen  present  in  the  water.  Both 
results  are  given  in  this  example. 

Notes 

The  estimation  of  the  amount  of  oxygen  dissolved  in  water  is 
of  some  value,  as  the  oxygen  becomes  much  diminished  in  the 
presence  of  organic  matter.  A  low  figure  for  dissolved  oxygen  is, 
at  least,  confirmatory  evidence  in  condemning  a  water  of  which 
suspicion  is  entertained. 

When  decolourizing  with  thiosulphate  solution,  it  often 
happens  that  the  colour  returns  two  or  three  times.  The  estima- 
tion, therefore,  should  not  be  considered  as  completed  until  the 
water  remains  colourless  for  four  or  five  minutes. 

Although  the  thiosulphate  is  made  up  to  a  definite  strength,  it 
will  not  keep  constant ;  so  it  is  advisable  to  standardize  it  occa- 
sionally against  standard  potassium  permanganate. 


INTERPRETATION    OF   RESULTS  3S 

THE   INTERPRETATION   OF  AN  ANALYSIS  OF  WATER 

The  attention  of  the  Public  Health  Student  is  especially 
directed  to  the  importance  of  grasping  the  fundamental  prin- 
ciples laid  down  in  this  chapter ;  and  he  is  asked  to  give  very 
careful  attention  to  the  analyses  of  various  waters,  with  which  the 
lessons  of  this  chapter  are  illustrated. 

Every  water  sample  must  be  treated  on  its  own  merits,  and 
local  circumstances  and  the  history  of  the  water  must  be  taken 
into  consideration  before  the  analyst  gives  a  favourable  or  an 
adverse  judgment.  It  is  easy  to'  say  when  a  water  is  good ; 
equally  easy  to  determine  when  it  is  very  bad ;  but  often  ex- 
tremely difficult  to  decide  on  many  waters  which  are  neither 
excellent  nor  foul.  It  is  in  judgment  on  these  indifferent  waters 
that  a  student  will  be  most  troubled  ;  and  it  is  here  that  some 
knowledge  of  geology,  and  of  the  composition  of  waters  from 
various  strata,  will  be  of  use  to  him  in  deciding  whether  or  not 
the  sample  under  his  consideration  deviates  from  the  type  to 
which  it  should  conform. 

In  the  first  place  it  must  be  remembered  that  no  water  must 
be  passed  or  condemned,  unless  it  contain  poisonous  doses  of 
lead  or  copper,  on  any  single  figure  in  the  analysis.  All  the 
figures  must  be  taken  together ;  this  will  be  seen  by  the  follow- 
ing notes  upon  the  individual  estimations. 

Physical  Characters 

Almost  all  waters  used  for  drinking  purposes  have  excellent 
physical  characters.  The  colour  is  faintly  blue  as  seen  in  the 
two-foot  tube,  the  water  is  bright  and  free  from  opacity,  and  has 
no  smell  nor  taste.  Any  odour  or  opacity  should  at  once  arouse 
suspicion  about  the  sample.  If  the  water  is  brown  in  colour  this 
may  be  due  to  salts  of  iron,  or  to  the  colouring  matter  extracted 
by  the  water  from  peat  and  upland  surfaces.  There  should  be 
no  sediment,  or  very  little,  and  in  a  good  water  this  sediment 
should  contain  neither  epithelium  nor  hairs  nor  matter  of  obvious 
animal  origin. 

Total  Solids 

These  vary  very  much  in  different  samples  of  water.  Rain 
water  may  have  about  3  parts  per  100,000  of  total  solids, 
and  a  water  derived  from  the  greensand  as  much  as  no  parts 
per   100,000.      A  well,  polluted  by  sea  water,  may,  of  course, 


36  WATER   ANALYSIS 

show  still  higher  figures.  Generally  speaking,  a  good  drinking 
water  should  not  contain  more  than  loo  parts  per  100,000  of 
total  solids. 

On  ignition  some  of  these  total  solids  are  removed,  and  the 
proportion  removed  is  of  some  importance.  Salts,  except  for 
their  water  of  crystallization,  are  not  affected  by  ignition  ;  but 
organic  matter  present  is  driven  off.  If,  therefore,  there  is  much 
loss  on  ignition,  and  if  the  residue  shows  signs  of  blackening,  the 
sample  should  be  regarded  as  suspicious. 

REACTION    OF    THE    WATER 

Most  drinking  waters  are  alkaline.  Some,  however,  derived 
from  upland  surfaces,  may  be  acid,  and  even  markedly  so.  Now 
an  acid  water  will  dissolve  lead  pipes  and  take  lead  into  solution, 
greatly  to  the  detriment  of  the  consumer  :  so,  if  a  water  is  acid, 
search  should  be  made  for  lead,  and  the  water  condemned  if  this 
is  found  in  any  amount  exceeding  0*025  parts  per  100,000.  In 
itself,  and  without  the  lead,  an  acid  water  is  of  no  harm. 

HARDNESS 

The  hardness  of  a  water  is  not  of  very  great  hygienic  import- 
ance. It  is  maintained  by  many  medical  men  that  water  which 
is  excessively  hard,  say  above  30  parts  per  100,000,  causes  a 
certain  amount  of  dyspepsia,  and  a  water  containing  such  a 
degree  of  hardness  could  not  be  recommended  for  drinking  pur- 
poses. The  chief  objection  to  having  a  hard  water  is  a  purely 
economical  one.  It  is  said  that  since  Glasgow  has  been  supplied 
with  water  from  Loch  Katrine  the  saving  to  the  city  of  Glasgow 
in  soap  per  annum  has  been  about  ^30,000.  Speaking  generally, 
the  hardest  waters  are  those  which  are  derived  from  superficial 
wells.  The  softest  is  of  course  pure  rain  water.  The  average 
hardness  of  the  London  water  is  about  16  parts  per  100,000,  and 
this  is  looked  upon  generally  as  the  limit  of  hardness  for  a  water 
for  drinking  purposes. 

CHLORIDES 

The  sources  of  chlorides  in  water  are  various.  Rain  water, 
especially  when  collected  near  the  sea,  always  contains  traces  of 
salt.  Certain  geological  formations  also  contain  considerable 
quantities  of  chlorides.  This  being  so,  the  purest  water  would 
be  expected  to  contain  certain  traces  of  chlorides,  and  this  is 
found  to  be  invariably  the  case.      The  water  drawn  from  districts 


INTERPRETATION   OF   RESULTS  37 

in  which  there  are  manufactories,  such  as  alkah  works,  mines, 
etc.,  is  also  found  to  be  rich  in  chlorine.  Urine  contains  about 
1%  of  chlorides,  and  therefore  the  addition  of  sewage  to  any 
drinking  water  would  probably  raise  the  quantity  of  chlorine. 
In  considering  the  percentage  of  chloride  which  is  to  be  allowed, 
it  is  necessary  in  the  first  place  to  know  something  about  the 
geological  stratum  from  which  the  water  is  drawn. 

If  the  chlorine  content  of  a  water  is  found  to  be  uniform 
throughout  the  year,  any  deviation  from  the  usual  figure  may  well 
give  rise  to  suspicion  that  the  water  has  been  contaminated. 
Well  waters  from  the  chalk  and  limestone  generally  have  a 
chlorine  figure  not  over  3  parts  per  100,000;  from  the  greensand 
and  some  of  the  marls,  and  in  the  neighbourhood  of  salt  mines 
or  the  sea,  the  chlorine  figure  may  be  very  high.  Rain  water 
collected  in  or  near  towns  contains  more  chlorine  than  that 
collected  in  the  open  country. 

FREE    AND    SALINE    AMMONIA 

Waters  from  all  sources  contain  ammonia.  Even  rain  water 
from  the  country  shows  some  traces.  Many  very  pure  waters 
from  deep  wells  have  large  quantities  of  ammonia,  which  is 
derived  from  the  reduction  of  nitrates  and  nitrites  :  the  green- 
sand  waters  are  examples  of  this.  Speaking  generally,  free  and 
saline  ammonia  should  not  exceed  0*005  P^^rts  per  100,000.  If 
it  exceeds  this,  the  albuminoid  ammonia  figure  should  be  low. 
Water  which  is  derived  from  rivers,  sewage,  or  known  polluted 
sources  contains  large  quantities  of  ammonia. 

ALBUMINOID    AMMONIA 

It  will  be  understood  from  what  has  been  said  in  the  sections 
on  the  actual  analysis  of  water  that  the  albuminoid  ammonia 
does  not  exist  as  such  in  the  water,  but  is  simply  a  laboratory 
product  from  the  organic  matter  present  in  the  water.  From  this 
it  will  be  seen  that  even  where  albuminoid  ammonia  exists  in 
considerable  quantities,  there  is  no  method  of  determining 
whether  the  organic  material  present  in  the  water  is  derived  from 
vegetable  or  animal  sources.  Nor  is  the  amount  of  albuminoid 
ammonia  found  in  the  water  a  very  accurate  test  of  the  amount 
of  organic  material  present  in  the  water.  Waters  which  are 
derived  from  deep  wells,  or  even  from  surface  wells  where  there 
is  no  possibility  of  contamination,  do  not,  however,  yield  much 
albuminoid  ammonia.      Indeed,  many  deep  well  waters,  that  is 


38  WATER   ANALYSIS 

waters  derived  from  beneath  the  impervious  layers,  contain  prac- 
tically no  albuminoid  ammonia  at  all.  The  consideration, 
however,  of  the  quantities  of  free  ammonia  and  albuminoid 
ammonia  together,  often  gives  a  good  clue  to  the  presence  or  no 
of  contamination. 

As  a  rule  the  figure  for  albuminoid  ammonia  should  not 
exceed  0*005  parts  per  100,000.  If  it  exceeds  this,  the  figure  for 
free  and  saline  ammonia  should  be  low.  In  other  words,  the  free 
ammonia  and  the  albuminoid  ammonia  should  not  both  be  high 
in  a  water;  if  the  one  is  raised,  the  other  should  not  also  exceed 
the  standard. 

The  albuminoid  ammonia  figure  is  high  in  waters  that  have 
been  polluted  with  animal  matter ;  and  is  also  raised  in  upland 
surface  waters,  in  which  latter  case  the  free  ammonia  figure  is 
invariably  low. 

NITRITES 

Nitrites  may  be  found  in  waters  that  have  been  polluted  by 
sewage  or  excrement.  Lower  greensand  waters  also  may  contain 
nitrites  from  the  reduction  of  nitrates  by  the  ferrous  salts  of  the 
stratum.  Unless  it  can  be  shown  that  nitrites  are  present  in 
a  drinking  water  in  consequence  of  such  reduction  of  nitrates,  the 
water,  if  it  contains  even  traces  of  any  nitrites,  must  be  considered 
as  highly  suspicious. 

NITRATES 

Nitrates  may  be  regarded  as  one  of  the  end  products  of  the 
oxidation  of  organic  matter,  and  their  presence  in  water  is  there- 
fore an  index  of  past  organic  contamination.  Certainly,  the 
organic  contamination  may  be  very  remote,  and  the  nitrate  may 
have  been  produced  many  years  before  the  water  comes  to  be 
analysed.  If  the  other  figures  of  the  analysis  are  good,  and  the 
nitrate  figure  is  high,  this  excess  over  the  average  may  be 
accounted  for  by  the  nitrates  in  the  stratum,  and  is  of  little  con- 
sequence ;  but  if  the  rest  of  the  analysis  throws  doubt  upon  the 
water,  a  raised  nitrate  figure  (together,  possibly,  with  increased 
chlorine)  will  turn  the  balance  against  the  water  under  considera- 
tion. Some  geological  strata  contain  nitrates  in  considerable 
degree,  but  a  large  proportion  of  nitrates  is  by  no  means  so 
common  as  in  the  case  of  chlorine.  Peaty  upland  waters  and 
waters  derived  from  the  Liassic  strata  may  be  rich  in  nitrates  ; 
but,  speaking  as  a  rule,  to  which,  of  course,  there  are  notable 
exceptions,  a  good  drinking  water  ought  not  to  contain  more 
than  o'5  parts  per  100,000  of  nitric  nitrogen. 


INTERPRETATION    OE   RESULTS 


39 


Oxygen  Absorbed  from  Permanganate 

Waters  which  contain  a  considerable  amount  of  organic 
material  absorb  an  amount  of  oxygen  which  to  some  degree 
corresponds  to  the  organic  material  present.  Organic  material 
animal  in  origin  absorbs  oxygen  more  readily  than  does  that 
derived  from  vegetable  sources.  If  this  were  all,  the  oxygen 
process  would  be  an  extremely  valuable  one,  but  unfortunately 
this  is  not  the  case.  Certain  other  matters,  particularly  the  proto- 
salts  of  iron,  etc.,  will  absorb  oxygen  when  in  a  water  containing 
absolutely  no  organic  material.  If,  therefore,  any  of  these  salts 
are  present,  a  considerable  allowance  must  be  made  for  the 
amount  of  oxygen  absorbed,  and  if  in  the  water  any  sediment  is 
present  which  consists  of  these,  the  water  must  be  carefully 
filtered  before  being  submitted  to  the  process. 

Frankland  and  Tidy  give  the  following  table,  which  may  be 
useful  as  forming  some  standard  to  which  waters  should  comply 
in  regard  to  the  oxygen  absorbed. 

Amounts  of  Oxygen  Absorbed  by  100,000  Parts  of  Water 


Water  from  Upland 
Surfaces. 

Water  from  Sources 

other  than  Upland 

Surfaces. 

Water  of  great  organic 

purity 
Water  of  medium  purity 
Water  of  double  purity 
Polluted  water 

Not    more    than    o'l 
0-3 
0-4 

More  than               0*4 

Not    more    than   0*05 
015 

More  than              0*2 

Examples  of  Waters  from  various  Sources 

The  first  two  analyses  given  are  those  of  a  very  good  and  a  very 
bad  water  respectively  ;  the  remainder  are  analyses  of  waters  from 
different  sources  and  from  some  of  the  main  water-bearing 
geological  strata  in  this  country. 

Analyses  3-16  inclusive  show  uncontaminated  waters;  17-22 
show  some  river  water  analyses;  and  23-30  are  analyses  of 
waters  that  are  contaminated.  In  the  light  of  what  has  already 
been  said   in    this   chapter,   the  careful  consideration   of  these 


40 


WATER   ANALYSIS 


various    analyses    should    do    much    to    help   the   student   to 
appreciate  the  significance  of  the  analytical  figures. 


No.  I 

No.  2 

A  very  good  water. 

A  very  bad  water. 

Physical  characters 

Excellent 

Excellent 

Reaction 

Slightly  alkaline 

Very  alkaline 

Total  solids  . 

i6'4 

42-8 

Volatile  . 

3-8 

20-3 

Appearance  on  igni- 

tion 

Nil 

Marked  blackening 

Hardness 

9-2 

30 

Chlorine 

^'3    0 

6-2 

Free  and  saline  ammonia 

o*ooo8 

0-030 

Albuminoid  ammonia    . 

O'OOI 

0  018 

Nitrites 

Nil 

A  trace 

Nitrates 

0"0I 

o'96 

Oxygen   absorbed   in   4 

hours  at  27°  C.  . 

O'OI 

0-34 

Notes  on  i  and  2 

All  figures  represent  parts  per  100,000.     These  two  waters  are 
^ood  examples  of  the  extremes  of  which  it  is  easy  to  judge. 


No.  3 

No.  4 

Rain  water— country. 

Rain  water — town. 

Physical  characters 

Excellent 

Good 

Reaction 

Faintly  alkaline 

Slightly  acid 

Total  Solids  . 

3-2 

5'i 

Volatile  . 

17 

27 

Appearance  on  igni- 

tion 

Nil 

Nil 

Hardness 

o"5 

07 

Chlorine 

0-31 

1*2 

Free  and  saline  ammonia 

0*042 

0-058 

Albuminoid  ammonia    . 

0-003 

0-005 

Nitrites 

Nil 

Nil 

Nitrates 

001 

004 

Oxygen   absorbed   in    4 

hours  at  27°  C.  . 

0*004 

0  022 

INTERPRETATION    OF   RESULTS 


41 


Notes  on  3  and  4 

Both  these  waters  show  the  low  total  solids  and  the  low  figure 
for  hardness  characteristic  of  rain  water.  The  free  ammonia 
figure  is  high  in  each ;  but  the  albuminoid  ammonia  and  the 
oxygen  absorbed  are  low,  showing  the  freedom  of  these  waters 
from  much  organic  matter.  Obviously,  No.  3  is  a  better  water 
than  No.  4. 


No.  5 

No.  6 

Upland  surface  water,  not 

Upland  surface  water, 

peaty. 

peaty. 

Physical  characters 

Good 

Brown 

Reaction 

Neutral 

Acid 

Total  solids . 

5'o 

lO'O 

Volatile  . 

17 

r^ 

Appearance  on  igni- 

tion 

Nil 

Blackening 

Hardness 

2-9 

3 '4 

Chlorine 

o'9 

0-9 

Free  and  saline  ammonia 

0*003 

O'OOI 

Albuminoid  ammonia    . 

0*004 

0'020 

Nitrites 

Nil 

Nil 

Nitrates 

o'o6 

o'04 

Oxygen  absorbed  at  27° 

C.  in  4  hours     . 

0-05 

■     o'i4 

Notes  on  5  and  6 

Both  these  waters  show  low  figures  for  hardness  and  for  total 
solids,  although  No.  6  gives  slightly  higher  readings  in  these 
respects  than  No.  5.  No.  5  really  is  very  much  like  the  rain 
water  analyses  shown,  except  that  the  ammonia  figure  is  less. 
No.  6  is  typical  of  peaty  waters,  being  acid  and  having  a  high 
figure  for  volatile  sohds  :  these  latter  it  is  noticed  show  charring 
on  ignition,  and  are  composed  of  organic  matter  derived  from 
the  peat.  The  high  figure  for  albuminoid  ammonia  is  due  to 
this  vegetable  organic  matter.  Note  that  in  No.  6  the  figure  for 
free  ammonia  is  low.  Both  waters  were  free  from  contamination 
with  animal  organic  matter. 


42 


WATER   ANALYSIS 


No.  7 

Subsoil  water.     Shallow 
well  in  Sand. 

No.  8 

Subsoil  water.     Shallow 
well  in  Gravel. 

Physical  characters 

Reaction 

Total  solids  . 

Volatile 

Appearance  on  ignition 
Hardness 
Chlorine 

Free  and  saline  ammonia 
Albuminoid  ammonia    . 
Nitrites 
Nitrates 

Oxygenabsorbed  at  27°C. 
in  4  hours 

Excellent 

Alkaline 

8-5 

27 

Nil 
57 

2  O 

Trace 

o'oo5 
Nil 

O'OI 

007 

Excellent 
Alkaline 

32-2 

10  I 

Nil 

25 '5 

2-0 

Trace 
0  '0005 

Nil 
0-51 

001 

Notes  on  7  and  8 

Both  these  are  very  good  waters.  They  show  low  ammonia 
figures,  and  low  figures  for  the  oxygen  absorbed  from  perman- 
ganate. No.  7  does  not  show  so  much  hardness  as  most  shallow 
well  waters  ;  No.  8,  however,  is  very  hard.  The  nitrate  figure  of 
No.  8  is  high,  but  of  little  import  since  the  water  is,  in  other 
respects,  so  excellent :  probably  these  nitrates  are  from  some  very 
old  organic  pollution  of  the  gravel  from  which  the  water  was  drawn. 
Shallow  well  waters  are  not  usually  so  pure  as  these,  and  have 
frequently  much  larger  quantities  of  ammonia,  both  free  and 
albuminoid. 


No.  9 

No.  10 

Deep  well  in  the  Chalk. 

Deep  well  in  the  Chalk. 

Physical  characters 

Excellent 

Excellent 

Reaction 

Alkaline 

Alkaline 

Total  solids  . 

26-5 

35  7 

Volatile 

9-0 

io"4 

Appearance  on  ignition 

Nil 

Nil 

Hardness 

20  "4 

2 1  6 

Chlorine 

I  "5 

17 

Free  and  saline  ammonia 

o"ooo5 

00015 

Albuminoid  ammonia    . 

o'ooo5 

O'COI 

Nitrites 

Nil 

Nil 

Nitrates 

o'4i 

0*27 

Oxygen  absorbed  in  4 

hours  at  27°  C. 

O'OI 

0-03 

INTERPRETATION    OF   RESULTS 


43 


Notes  on  9  and  10 

Both  of  these  are  excellent  chalk  waters  in  which  the  hardness 
is  fairly  high  :  about  half  this  hardness  is  temporary  and  can  be 
removed  by  appropriate  softening  processes.  The  chlorides  and 
nitrates  are,  of  course,  derived  from  the  strata  through  which  the 
water  has  passed.  The  ammonia  figures  and  the  oxygen  absorbed 
are  low.  Some  chalk  waters  contain  much  more  total  solids 
than  do  these. 


No.  n 

No.  12 

Upper  Grcensand. 

Lower  Greensand. 

Physical  characters 

Excellent 

Good 

Reaction 

Alkaline 

Alkaline 

Total  solids 

13-1 

106  0 

Volatile 

3'o 

21-4 

Appearance  on  igni- 

tion 

Nil 

Nil 

Hardness 

5-8 

i8-o 

Chlorine 

2-0 

117 

Freeandsaline  ammonia 

Trace 

0-038 

Albuminoid  ammonia    . 

o-ooi 

O'OOI 

Nitrites 

Nil 

Trace 

Nitrates 

0*25 

0-30 

Oxygen      absorljed     at 

27"  C.  in  4  hours 

Nil 

0*36 

Notes  on  11  and  12 

No.  1 1  is  obviously  an  excellent  water,  and  otherwise  has  no 
special  characteristics.  No.  12,  at  first  sight,  might  seem  to  be 
much  polluted  :  the  free  ammonia  figure  is  high,  and  the  chlorides 
are  excessive,  moreover  nitrates  are  present.  This  water  on 
analysis  showed  a  trace  of  iron,  and  to  the  reducing  properties  of 
this  metal  the  figures  on  which  I  have  commented  are  due.  The 
nitrites  are  formed  by  the  reduction  of  nitrates,  and  so  is  the 
free  ammonia  :  the  high  chlorine  figure  is  typical  of  some  green- 
sand  waters.  Note  the  small  amount  of  albuminoid  ammonia, 
which  points  to  the  absence  of  organic  pollution. 


44 


WATER   ANALYSIS 


No.  13 

No.  14 

Oolite. 

New  Red  Sandstone. 

Physical  characters 

Excellent 

Excellent 

Reaction 

Alkaline 

Alkaline 

Total  solids 

74*6 

33 '5 

Volatile  . 

18 -2 

9-1 

Appearance  on  igni- 

tion 

Nil 

Nil 

Plardness 

27 

22-8 

Chlorine 

2 '2 

2-8 

Freeand  saline  ammonia 

o'oco4 

Trace 

Albuminoid  ammonia    . 

Trace 

Trace 

Nitrites 

Nil 

Nil 

Nitrates 

O'Ol 

0'25 

Oxygen      absorbed  .  at 

27°  C.  in  4  hours 

o"oo8 

Nil 

Notes  on  13  and  14 

Both  these  are  very  good  waters.  No.  13  from  the  Oolite  is 
very  similar  in  composition  to  a  chalk  water.  No.  14  is  better 
than  most  sandstone  waters  :  these  vary  greatly  in  their  com- 
position, depending  on  the  nature  of  red  sandstone  deposit, 
which  may  be  pure  or  impure,  soft  or  hard.  The  total  solids 
and  hardness  in  these  waters  may  in  consequence  be  sometimes 
very  high. 


No.  15 

No.  16 

Coal  Measures. 

Carboniferous  Limestone. 

Physical  characters 

Excellent 

Excellent 

Reaction 

Alkaline 

Alkaline 

Total  solids  . 

559 

30  "4 

Volatile  . 

147 

87 

Appearance  on  igni- 

tion 

Nil 

Nil 

Hardness 

357 

2i 

Chlorine 

I '2 

17 

Freeand  saline  ammonia 

o'oo6 

0'002 

Albuminoid  ammonia    . 

0'002 

O'OOI 

Nitrites 

Nil 

Nil 

Nitrates 

o"oo4 

0*27 

Oxygen       absorbed      at 

27°  C.  in  4  hours 

0-4 

0056 

INTERPRETATION    OF   RESULTS 


45 


Notes  on  15  and  16 

Both  these  waters  are  of  good  quality,  as  far  as  absence  of 
organic  pollution  is  concerned.  No.  15  is  exceptionally  hard, 
and  for  that  reason  would  make  the  water  unfitted  for  trade 
purposes,  unless  some  softening  process  were  adopted. 


River  Waters 

may   be   divided   into    two   classes- 


-{a)    those 


River  waters 
affected  by  the  tide  and  {b)  those  not  so  affected. 

The  first  class  will  obviously  show  the  variations  of  the  second 
class,  but  will  have  an  additional  variant  in  the  greater  or  less 
amount  of  sea  water  they  contain  at  any  moment. 

The  non-tidal  river  waters  will  vary  with  the  sources  from 
which  they  are  derived.  In  the  upper  reaches  the  rivulets  may 
consist  of  either  upland  surface,  subsoil  or  deep  well  water,  the 
two  latter  appearing  as  springs.  In  their  lower  reaches  most 
probably  all  rivers  consist  of  a  mixture  of  all  three,  in  different 
proportions  in  different  rivers.  All  rivers  drain  the  subsoil  water 
of  their  basins. 

In  the  following  table  these  differences  are  well  seen  : — 

RIVER  WATERS 


No. 

Source. 

Parts  per  100,000 

m 

0 

H 

tn 

n 

0 

H 

.s 

U 

.s 

"o 
c 

's 

0 

< 

V 

125 

0 

0 

c 

4) 

bO 

>! 

X 

0 

17 
18 

19 
20 
21 
22 

Scotland     . 
Westmorland 
Devon 
Worcester  . 
V^^ilts 

4"i 
4-3 

23-1 

54-5 
70-2 

2-4 
2-4 

27 

iro 
38-8 
51-4 

I"0 

i-o 
I"I 

5-8 
2-4 

2*2 

Trace 

•008 

Trace 

•013 

Trace 

•004 

•005 
•015 
•005 
•022 
•076 
'01 

Nil 
Nil 
Nil 
Nil 
Nil 
Nil 

Nil 
Trace 
Trace 

•07 
Trace 

•09 

•18 

•15 
•05 

•44 
•13 

•14 

Notes  on  17-22 

No.  17  is  a  pure  water.  No.  18  shows  evidence  of  organic 
contamination,  which  is  possibly  vegetable  in  origin.  No.  19 
is  a  pure  water.  No.  20  is  very  foul.  Nos.  21  and  22  show 
much  hardness,  and  high  figures  for  the  albuminoid  ammonia. 


46 


WATER   ANALYSIS 


The   following    eight    analyses    are    those    of    contaminated 
waters  : — 


No.   23 

No.  24 

Upland  surface,  peaty 

Shallow  well  — 

water. 

Sand. 

Physical  characters 

BfDwn 

Excellent 

Reaction 

Acid 

Alkaline 

Total  solids  . 

162 

13-1 

Volatile  . 

I2"I 

8-2 

Appearance  on  igni- 

tion 

Blackening 

Slight  blackening 

Hardness 

2-8 

5'0 

Chlorine 

I '5 

2*2 

Free  and  saline  ammonia 

o'ooS 

0-013 

Albuminoid  ammonia    . 

0'026 

0-033 

Nitrites 

Nil 

Nil 

Nitrates 

0-35 

0-47 

Oxygen      absorbed      at 

27°  Cjin  4  hours 

0-46 

053 

Notes  on  23  and  24 

Both  these  waters  are  bad.  Each  shows  high  ammonia  figures, 
increased  nitrates  and  an  excessive  amount  of  oxygen  absorbed 
from  permanganate.  Moreover,  No.  23  shows  a  chlorine  figure 
that  is  considerably  above  what  is  usually  found  in  upland  surface 
waters.  Note  that  both  these  waters  show  some  blackening 
when  their  total  solids  are  ignited. 


No.  25 

No.  26 

Shallow  well  in  gravel. 

Shallow  well  in  gravel. 

Physical  characters 

Slightly  turbid 

Excellent 

Reaction 

Alkaline 

Alkaline 

Total  solids 

24  6 

467 

Volatile  . 

io'6 

16-9 

Appearance  ^n  igni- 

tion 

Marked  blackening 

Nil 

Hardness 

136 

285 

Chlorine 

27 

5 '9 

Freeand  salineammonia 

O'OIO 

0"00I 

Albuminoid  ammonia    . 

0"022 

0"002 

Nitrites 

Nil 

Nil 

Nitrates 

O'QI 

I  "95 

Oxygen      absorbeil      at 

27°  C.  in  4  hours 

0'20 

o-i8 

INTERPRETATION   OF   RESULTS 


47 


Notes  on  25  and  26 

No.  25  is  an  analysis  of  a  badly  contaminated  water,  as  shown  by 
the  blackening  of  the  total  solids  on  ignition  and  by  the  raised 
figures  for  the  ammonia  and  nitrates.  No.  26  shows  an  analysis 
ofa  well  water  that  has  been  heavily  polluted  in  the  past;  but 
which  has  oxidized  almost  all  the  organic  matter  into  nitrates. 
The  chlorine  figure  for  this  well  is  also  high,  and  the  nitrates,  of 
course,  excessive.  This  water  is  potentially  very  dangerous  :  it 
was  badly  contaminated  once,  and  there  is  no  reason  why  this 
should  not  happen  again. 


No.  27 

No.  28 

Shallow  well  in  Chalk. 

Deep  well  in  Chalk. 

Physical  characters 

Excellent 

Excellent 

Reaction 

Alkaline 

Alkaline 

Total  solids  . 

60 -o 

72-8 

Volatile  . 

22*1 

26*4 

Appearance  on  igni- 

tion 

Slight  blackening 

Nil 

Hardness 

23 '4 

200 

Chlorine 

2-8 

2*1 

Free  and  salineammonia 

0*007 

o'oo6 

Albuminoid  ammonia    . 

o"oo8 

0-005 

Nitrites 

Nil 

Nil 

Nitrates 

0-84 

0*52 

Oxygen     absorbed      at 

27°  C.  in  4  hours 

0-093 

0*07 

Notes  on  27  and  28 

The  shallow  well  water.  No.  27,  shows  increased  ammonia 
figures  and  high  nitrates.  The  well  was  near  a  heap  of  manure, 
and  water  percolated  from  this  through  the  subsoil  and  so  into 
the  well,  the  sides  of  which  were  not  protected.  No.  28  shows 
the  analysis  of  a  deep  well  chalk  water,  which  was  liable  to  inter- 
mittent contamination  through  defects  in  the  stratum.  Although 
the  figures  for  No.  28  are  not  in  themselves  very  excessive,  they 
are  greatly  above  the  average  for  this  well,  in  the  waters  of  which 
albuminoid  ammonia  usually  occurs  only  as  a  trace.  The  normal 
chlorine  figure  for  this  well  is  i  '8. 


48 


WATER   ANALYSIS 


No.  29 

No.  30 

Deep  well  in  Chalk. 

Deep  well  in  Chalk. 

Physical  characters 

Excellent 

Brackish  taste 

Reaction 

Alkaline 

Alkaline 

Total  solids . 

40-4 

272-4 

Volatile  . 

127 

36-0 

Appearance  on  igni- 

tion 

Faint  blackening 

Faint  blackening 

Hardness 

20"5 

50 

Chlorine 

17 

120-4 

Free  and  saline  ammonia 

0-002 

o'oo5 

Albuminoid  ammonia    . 

0-003 

0*002 

Nitrites 

Nil 

Nil 

Nitrates 

0-32 

I -07 

Oxygen      absorbed      at 

27"  C.  in  4  hours 

0-05 

0-071 

Notes  on  29  and  30 

No.  29  looks  like  the  analysis  of  a  good  water.  Normally, 
however,  the  chlorine  content  of  this  water  is  1-5,  and  the 
nitrate  figure  0-22.  Usually  there  are  only  traces  of  albuminoid 
ammonia,  the  saline  ammonia  is  less  than  q-qoi,  and  no  oxygen 
is  absorbed  from  permanganate.  With  the  knowledge  of  this 
past  history,  we  can  condemn  water  No.  29  as  showing  organic 
contamination.  The  analysis  No.  30  is  of  a  deep  well  water  near 
a  tidal  river.  In  times  of  flood  and  high  tides  some  of  the  salt 
water  finds  its  way  into  the  well,  as  is  shown  by  the  analysis. 

In  an  examination,  or  where  the  student  is  required  quickly 
to  complete  a  water  analysis,  it  is  satisfactory  to  have  a  plan  of 
work,  and  to  adhere  rigorously  to  this ;  by  so  doing,  labour  is 
saved  and  the  worker  is  spared  from  having  to  improvise  on  a 
sudden  some  scheme  of  his  own. 

The  following  order  of  performing  the  various  analyses  of  a 
water  sample  can  be  recommended  :  it  is  put  forward  as  a  useful 
scheme,  but  not  necessarily  the  best.  Whether  the  student 
adopts  this  or  some  other,  let  him  adhere  to  one  only ;  for  by  so 
doing  he  will  save  himself  much  confusion,  and  be  able  the 
better  to  co-ordinate  his  work. 

I.  Examine  the  physical  properties  of  the  water.  Start  the 
water  evaporating  for  the  estimation  of  the  total  solids  ;  start 
some  more  boiling  for  the  estimation  of  permanent  hardness. 


A  SCHEME  OF  PRACTICAL  WORK         49 

Set  up  and  start  the  apparatus  for  estimating  free  and  saline 
ammonia.  Set  some  water  boiling  to  concentrate  for  testing  for 
poisonous  metals.     Start  Tidy's  process. 

2.  Test  for  nitrites  and  nitrates. 

3.  If  nitrates  are  present  start  the  phenol-sulphonic  acid 
method  of  their  estimation. 

Note 

All  the  lengthy  processes  have  now  been  begun.  The  student 
can  now  perform  various  smaller  manipulations  until  the  free 
ammonia  begins  to  come  over. 

4.  Estimate  the  chlorine.  Estimate  the  nitrites,  if  such  are 
present.  Estimate  the  total  hardness.  Using  the  water  that  has 
been  boiling,  estimate  the  permanent  hardness.  Calculate  the 
temporary  hardness,  and  make  notes  of  all  your  results. 

5.  The  free  and  saline  ammonia  should  have  distilled  over  by 
now.     Start  the  distillation  of  the  albuminoid  ammonia. 

6.  Estimate  the  free  and  saline  ammonia. 

7.  The  phenol-sulphonic  acid  method  should  now  be  ready 
for  completion.     Finish  this. 

8.  Test  the  concentrated  water  for  the  poisonous  metals.  If 
present,  estimate  them. 

9.  The  albuminoid  ammonia  will  now  be  distilled  off. 
Estimate  it. 

10.  Weigh  the  total  solids.  Ignite  and  weigh  the  residue  of 
non-volatile  solids. 

11.  Finish  off  Tidy's  method. 

Note 

The  wise  student  takes  to  examinations  with  him  porcelain  or 
platinum  dishes  of  known  weight.  By  so  doing  he  saves  much 
time  and  trouble.  All  results  should  be  noted  as  they  are 
obtained,  and  the  last  hour  of  the  examination  should  be  devoted 
to  careful  revision  of  the  results  and  to  the  writing  of  the  report. 

In  all  practical  examinations  it  is  impossible  to  over-estimate  the 
importance  of  the  written  part,  for  it  is  by  this,  very  largely,  that 
the  examiner  judges  of  the  candidate's  grasp  of  the  practical 
work.  In  the  case  of  a  water  examination,  the  report  should  be 
written  and  arranged  as  if  it  were  issued  from  the  laboratory  of  a 
public  analyst,  and  should  be  headed  after  the  following 
manner :  "  Report   on  sample  of  water  marked  X,  received  on 


50  SEWAGE  ANALYSIS 

such  a  date  and  examined  on  such  a  date."     Then  should  follow 
details  of  the  source  of  the  water,  if  this  is  known. 

Workers  in  laboratories  should  aim  at  order  and  cleanliness  in 
their  methods.  A  messy  and  untidy  bench  does  not  impress  an 
examiner  favourably. 


SEWAGE    ANALYSIS 

The  composition  of  sewage  varies  within  wide  limits.  Some 
towns  have  abundance  of  water  to  dilute  their  sewage ;  others 
have  little  ;  others,  again,  discharge  trade  refuse  of  every  con- 
ceivable description  into  the  sewers.  There  is  no  such  thing  as 
a  standard  sewage,  for  no  two  are  alike.  Even  in  one  town  or 
village  the  sewage  varies  in  composition  from  day  to  day  and 
from  hour  to  hour. 

In  making  a  chemical  analysis  of  sewage,  the  procedure 
described  under  water  is  adopted,  but  with  slight  modifications. 

TOTAL   SOLIDS 

These  may  be  estimated  in  two  ways.  The  total  solids  both  in 
suspension  and  solution  may  be  estimated,  or  a  portion  of  the 
sewage  may  be  filtered.  The  residue  is  dried,  weighed,  and  sub- 
sequently ignited,  and  the  loss  on  ignition  noted ;  the  filtrate  is 
then  evaporated  to  dryness,  dried,  weighed,  and  subsequently 
ignited  and  weighed  again. 

Chlorides 

The  chlorides  of  a  sewage  will  be  found  to  vary  considerably. 
They  are  estimated  in  the  way  already  described. 

Saline  Ammonia 

As  this  is  usually  very  high,  often  as  high  as  i  to  2  parts  per 
100,000,  and  sometimes  much  higher,  it  is  obvious  that  it  will  be 
useless  to  distil  500  c.c,  since  we  should  require  no  less  than 
500  c.c.  of  standard  ammonia  to  match  the  distillates 


CRUDE   SEWAGE  51 

Before  determining  what  quantity  to  use  for  distillation  it  is 
useful  to  filter  a  little  of  the  sewage.  Take  10  c.c.  of  the  filtrate 
and  dilute  it  with  40  c.c.  of  ammonia-free  water  in  a  Nessler 
glass.  Then  add  2  c.c.  of  Nessler  and  match  this  with  the 
standard  ammonia.  If  the  ammonia  required  is  less  than  10  c.c, 
use  20  c.c,  and  if  more,  use  10  c.c. 

Suppose  we  decide  to  use  20  c.c  Pipette  20  c.c  of  the 
sewage  into  the  retort  or  flask  and  add  half  a  litre  of  organically 
pure  ammonia-free  water. 

At  this  stage  the  reaction  of  the  sewage  should  be  determined, 
since  in  some  places  where  the  refuse  matter  from  chemical 
works  accompanies  the  domestic  sewage,  it  may  be  neutral  or 
even  slightly  acid.  If  it  is  not  found  to  be  distinctly  alkaline,  a 
very  small  quantity  of  freshly  fused  Na^COs  should  be  added, 
just  sufficient  to  render  it  faintly  alkaline. 

The  distillation  is  now  proceeded  with  as  in  the  case  of 
ordinary  water. 

Instead  of  estimating  the  amount  of  ammonia  in  each  50  c c, 
the  first  200  c.c.  may  be  collected  in  a  flask  and  well  shaken. 
20  c.c.  of  this  may  then  be  estimated  and  the  result  multiplied 
by  10. 

Albuminoid  Ammonia 

When  all  the  saline  ammonia  has  come  over,  the  alkaline  per- 
manganate solution  is  added,  and  the  distillation  proceeded  with 
in  the  ordinary  manner. 

Instead  of  merely  adding  50  c.c  of  alkaline  permanganate 
it  is  advisable  to  dilute  this  with  as  much  as  200  c.c  or 
250  c.c  of  distilled  water  and  boil  the  mixture  well  for  a  few 
minutes.  By  doing  this  there  is  much  less  chance  of  the  flask 
boiling  dry,  since  it  often  happens  that  12  or  14  Nessler  glasses 
are  collected  before  the  yield  of  ammonia  ceases. 

It  is  better  to  estimate  the  organic  nitrogen  by  Kjeldahl's 
method,  as  is  described  later. 


Nitrites 

It  is  generally  found  that  the  reaction  for  nitrites  is  either  not 
given  or  only  very  faintly.  This  is  probably  due  to  the  fact  that 
as  fast  as  they  are  formed  by  reduction  of  the  nitrates  they  are 
entirely  reduced  to  ammonia. 


52  SEWAGE   ANALYSIS 

Nitrates 

These  salts  are  present  only  in  minute  traces.  The  reducing 
power  of  sewage  is  very  great,  so  whatever  nitrates  are  present 
are  reduced  rapidly  to  ammonia.  The  indigo  method  of  estimat- 
ing the  nitrates  should  be  used,  and  there  is  seldom  any  need 
previously  to  dilute  the  sewage. 

Oxygen  Absorbed 

20  c.c.  is  a  very  convenient  quantity  to  take  for  this  examina- 
tion. 1 80  c.c.  of  organically  pure  ammonia-free  water  are  added 
and  the  usual  10  c.c.  of  standard  permanganate.  Even  with  so 
small  a  quantity  as  20  c.c.  it  sometimes  happens  that  a  further 
10  c.c.  of  permanganate  are  required. 

Dissolved  Oxygen 

The  dissolved  oxygen  figure  for  sewage  and  for  sewage  effluents 
can  be  determined  by  the  method  of  Winkler,  which  has  already 
been  described. 

The  analysis  of  sewage  effluents  should  be  carried  out  on  the 
same  lines  as  laid  down  for  crude  sewage.  The  solids  in  suspen- 
sion should  be  estimated ;  also  the  chlorides,  nitrites,  nitrates, 
and  free  ammonia.  The  albuminoid  ammonia  should  be  deter- 
mined by  Kjeldahl's  method,  as  the  ordinary  means  do  not  give 
reliable  results. 

Total  Nitrogen  (exclusive  of  nitrites  and  nitrates) 

KJELDAHL'S    METHOD 
Apparatus,  etc.,  required 

1.  200  c.c.  flask  of  Jena  glass. 

2.  750  c.c.  distilling  flask. 

3.  Glass  tube  bent  to  a  convenient  angle  with  a  bulb  blown  on 

the  vertical  arm. 

4.  Ordinary  flask. 

5.  Burette. 

6.  Concentrated  nitrogen-free  H0SO4. 

7.  Nordhausen  (or  fuming)  H.^SO^. 

8.  Crystals  of  pure  KMn04. 


SEWAGE   EFFLUENTS  53 

9.  KOH  solution  50%. 

10.  ^  HCl  or  ILSO.  and  ^NaOH. 

11.  Phenolphthalein  or  rosolic  acid. 

The  Process 

1.  Pipette  10  c.c.  of  the  sewage  into  the  small  flask,  add  about 

I  c.c.  of  H2SO4,  mix  well,  and  evaporate  slowly  over  a  small 
flame  guarded  by  wire  gauze. 

2.  When  the  fluid  is  reduced  to  rather  less  than  half,  add  20  c.c. 

of  H^SO^  and  3  c.c.  of  Nordhausen  HoSO^  and  continue  to 
heat  slowly. 

3.  From  time  to  time  add  a  small  crystal  of  KMnO^  until  the 

colour  disappears  very  slowly,  and  continue  the  heating  for 
about  3  hours. 

4.  Allow  the  contents  of  the  flask  to  cool,  and  carefully  transfer 

them  to  the  distilling  flask.  Wash  the  flask  with  a  small 
quantity  of  distilled  water  two  or  three  times  and  pour  the 
washings  into  the  distiUing  flask. 

5.  Add  70  c.c.  of  the  KOH  solution  and  allow  the  mixture  to 

cool.    After  cooling,  add  30  c.c.  more  of  the  KOH  solution, 

drop  in  two  or  three  pieces  of  clean  granulated  zinc  and 

carefully  insert  an  indiarubber  stopper.     Connect  the  flask 

by  means  of  rubber  tubing  with  the  bent  glass  tube  so  that 

the  free  end  dips  down  to  the  bottom  of  a  clean  Erlenmeyer 

.   .  N 

flask  contammg  50  c.c.  of  -^HgSO^,  the  bulb  being  a  little 

distance  above  the  mouth  of  the  flask. 

6.  Carefully  distil  until  the  residue  is  rather  less  than  half  the 

amount  of  the  original  fluid. 

7.  Remove  the  flask  containing  the   distillate,  add  a  drop  of 

N 
rosohc   acid,  and    add    the    -NaOH    carefully   until   the 

50 
reaction  is  neutral.     Read  ofl"  the  amount  of  alkali  required 
and  calculate  the  amount  of  NH3  therefrom,     ji  of  the 
ammonia  calculated  will  represent  the  nitrogen. 

Explanation 

Upon  boihng  nitrogenous  organic  matter  with  HoSO^  under 
the  conditions  above  described,  the  nitrogen  is  slowly  converted 


54  SEWAGE    ANALYSIS 

into  ammonium  sulphate.  When  the  process  of  conversion  is 
completed,  the  H.^SO^  is  over-neutralized  with  KOH,  and  free 
NHg  will  then  distil  over. 

EXAMPLE 
After  the  distillation  w^as  finished  it  was  found  that  the  50  c.c.  of 
— H,SO,  required  46-2  c.c.   of    — NaOH. 

•   7,  "8  c.c.  of  —  HoSO .  had  been  neutralized  by  the  NHo  distilled 
"  ^  SO     '      ' 

over 

.'.  N..  present  =  —  x  -^ x  0*34  gramme 

^  17      1000 

=  1  "06  milligrams. 

But  this  w'as  present  in  10  c.c.  of  the  sewage  effluent. 

.'.  the  sewage  effluent  contains  io"6  parts  per  100,000  of 
nitrogen. 

The  distillation  of  the  sew^age  effluent  showed  that  there  were 
10 '9  parts  of  saline  ammonia  per  100,000.  This  is  equivalent 
to  8"97  parts  of  nitrogen. 

Therefore  the  organic  nitrogen  in  the  sample  of  sew^age 
effluent  is  io-6  -  8-97  =  1*63  parts  per  100,000. 

Notes 

Great  care  must  be  exercised  in  heating  the  distilling  flask  at 
first,  since  there  is  a  great  tendency  for  the  fluid  to  "  bump." 
After  a  little  time  it  will  boil  quite  quietly  until  the  ammonia 
has  all  been  driven  off,  when  it  will  once  more  begin  to  bump. 

General  Considerations 

From  w^hat  has  been  said  of  the  varying  composition  of 
sewage,  it  may  be  inferred  that  sewage  effluents  also  show  much 
variation  :  and  this  is  indeed  the  case.  It  follows  from  this  that 
a  set  standard  of  purity  is  neither  obtainable  nor  desirable. 
Each  sewage  must  be  treated  on  its  own  merits,  and  the  local 
circumstances  taken  into  consideration  before  judgment  is  passed 
on  an  effluent. 

Whether  or  not  an  effluent  causes  harm  to  a  stream  depends 
mainly  on  two  factors  :  firstly,  on  the  quantity  and  concentration 
of  the  effluent ;  secondly,  on  the  size  and  volume  of  the  stream. 
It  is  obvious  that  an  effluent,  approaching  crude  sewage  in  com- 
position, would  do  much  more  harm  to  a  small  than  to  a  large 


SEWAGE    EFFLUENTS  55 

river ;  and,  again,  a  small  amount  of  a  sewage  effluent  would  do 
less  damage  than  a  larger  amount.  Doubtless  it  would  be  de- 
sirable to  have  local  standards  of  purification  for  sewage,  which 
standards  should  take  into  consideration  such  circumstances  as 
these;  and  whatever  standards  of  purity  were  established  they 
should  have  for  their  main  object  the  protection  of  rivers  from 
contamination  and  harm. 

The  injury  caused  to  a  river  by  the  inflow  of  sewage  or  a  bad 
effluent  may  be  considerable.  The  water  may  be  deprived  of  its 
oxygen,  and  the  fish  of  the  river  may  die  :  trade  refuse  may  cause 
a  like  mortality.  Organic  matter,  deposited  from  the  sewage, 
may  stink,  and,  ultimately,  silt  up  the  river  :  sewage  fungus  may 
grow  and  decay  :  the  river  may  be  discoloured.  Finally,  the 
water  may  be  poisoned  by  intestinal  organisms,  and  be  made 
unfit  for  drinking  purposes  to  the  detriment  of  cattle  and  man. 
An  effluent  should  not  be  discharged  into  a  stream  if  it  is  likely 
to  harm  the  water  in  any  of  these  ways. 

Satisfactory  Effluents 

The  Royal  Commission  on  Sewage  Disposal,  which  was 
appointed  in  1898,  consider  that  the  effect  which  an  effluent 
has  on  a  stream  does  not  depend  so  much  on  the  amount  of 
organic  matter  present,  as  on  the  condition  of  this  organic 
matter — whether  or  not  it  is  easily  putrescible,  and  is  likely  to 
take  up  oxygen  from  the  water. 

The  Commissioners  conclude  that  an  effluent  would  generally 
be  satisfactory  if  it  fulfilled  the  following  conditions  : — 

1.  That  it  should  not  contain  more  than  3  parts  per  100,000  of 

suspended  matter. 

2.  That    after  being  passed    through    filter-paper  it  should  not 

absorb  more  than — 

(a)  o"5  part  by  weight  per  100,000  of  dissolved  or  atmospheric 

oxygen  in  twenty-four  hours ;  or 
(d)  I'o  part  by  weight  per  100,000  of  dissolved  or  atmospheric 

oxygen  in  forty-eight  hours  ;  or 
(c)    1*5  parts  by  weight  per  100,000  of  dissolved  or  atmospheric 

oxygen  in  five  days. 

An  effluent  which  fulfils  these  conditions  will  probably  not  be 
putrescible. 

It  may  be  laid  down  as  a  physical  standard  for  all  sewage 
effluents    that    they    should    not    smell   nor    be  offensive   after 


56  SEWAGE    ANALYSIS 

incubation  for  three  days  at  2f  C.  Effluents  also  should  show 
Httle  opacity. 

In  contradiction  to  the  Sewage  Commissioners  some  author- 
ities consider  the  organic  ammonia  figure  to  be  the  best  index  of 
a  satisfactory  effluent.  A  limit  of  o*i  parts  per  100,000  has  been 
advocated  by  some  chemists  ;  o"i5  parts,  and  o'2  parts  by  others. 
Some  have  taken  the  oxygen  absorbed  figure  as  a  standard,  and 
said  that  no  sewage  effluent  ought  to  absorb  more  than  i'4  parts 
of  oxygen  per  100,000  from  permanganate. 

It  will  be  seen,  therefore,  that  really  there  is  no  chemical 
standard  for  a  sewage  effluent;  and  the  physical  standards,  com- 
bined with  the  incubation  tests,  are  the  best  means  at  the  present 
for  arriving  at  a  decision  as  to  the  suitability  of  an  effluent  for 
discharge  into  a  stream. 


PREPARATION    OF    REAGENTS 
Ammonia-free  Water 

The  following  process  is  most  usually  adopted : — 

Distil  from  a  large  glass  retort  (or  better,  from  a  copper  or 
tin  vessel  holding  15-20  litres)  ordinary  distilled  water  which  has 
been  rendered  distinctly  alkaline  by  the  addition  of  sodic  car- 
bonate. A  glass  Liebig's  condenser  or  a  clean  tin  worm  should 
be  used  to  condense  the  vapour ;  it  should  be  connected  to  the 
still  by  a  short  indiarubber  joint.  Test  the  distillate  from  time  to 
time  with  Nessler's  solution  (which  is  described  below),  and  when 
free  from  ammonia  collect  the  remainder  for  use.  The  collection 
of  water  must  be  stopped  when  at  least  2  litres  (in  such  a  sized 
still)  remain. 

Ammonia-free  Water— Organically  Pure 

Distilled  water,  to  which  i  gramme  of  potassium  hydrate  and  o.  2 
gramme  of  potassium  permanganate  per  litre  have  been  added,  -is 
boiled  gently  for  about  24  hours  in  a  similar  vessel  to  that  used 
in  preparing  water  free  from  ammonia,  a  redux  condenser  being 
fitted  on  to  the  top  of  the  flask  in  order  to  return  the  condensed 
water.  At  the  end  of  that  time  the  condenser  is  adjusted  in  the 
usual  way,  and  the  water  carefully  distilled,  the  distillate  being 


PREPARATION    OF    REAGENTS  $7 

tested  at  intervals  for  ammonia,  as  in  preparing  the  ordinary 
ammonia-free  water.  When  ammonia  is  no  longer  found,  the 
remainder  of  the  distillate  may  be  collected,  taking  care  to  stop 
well  short  of  dryness.  The  neck  of  the  retort  or  still  should 
point  slightly  upwards,  so  that  the  joint  which  connects  it  with 
the  condenser  is  the  highest  point.  Any  particles  carried  up 
mechanically  will  then  run  back  to  the  still,  and  not  contaminate 
the  distillate.  The  water  thus  obtained  should  be  rendered 
slightly  acid  with  sulphuric  acid,  and  redistilled  from  a  clean 
vessel,  again  stopping  short  of  dryness. 

Alkaline  Permanganate  Solution 

Dissolve  8  grammes  of  KMn04  and  200  grammes  of  NaOH  in 
1 100  c.c.  of  distilled  water.  Boil  until  the  bulk  is  reduced  to 
1000  c.c. 

The  object  of  the  boiling  is  to  drive  off  as  ammonia  any 
organic  matter  that  may  be  present,  either  in  the  permanganate 
or  the  water. 

Metaphenylene-diamine-hydrochloride 

I  gramme  of  the  base  is  dissolved  in  200  c.c.  of  distilled  water, 
and  slightly  acidulated  with  HCl. 

Nessler  Solution 

1.  Dissolve  35  grammes  of  KI        in    100  c.c.  of  NHg-free  HgO. 

2.  „        17        »         n  HgCl2  „    300    „         „  ,, 

3.  „      200      „         „  NaOH  ,,1000    „       „  „ 
The   HgCl2  dissolves  more  quickly  on  heating,   but  it  must 

be  subsequently  cooled. 

4.  Pour  the  HgCl2  solution  into  the  KI  solution  until  a  per- 

manent precipitate  of  Hgl2  is  formed. 

5.  Dilute  this  mixture  to    1000  c.c.  with  the  NaOH   solution. 

The  precipitate  will  be  re-dissolved. 

6.  Add   more  of  the  HgClg  solution  until  the  permanent  pre- 

cipitate is  again  formed. 

7.  Allow  the  mixture  to  stand  in  a  clean  glass-stoppered  bottle 

for  24  hours. 

8.  Pipette  off  the  clear  fluid  from  time  to  time  as  required. 

When  the  Nessler  is  sensitive,  it  has  a  slight  yellow  colour.  If 
it  is  colourless  it  will  not  be  sensitive,  and  a  little  more  HgClg 
solution  must  be  added  and  allowed  to  settle  in  order  to  saturate 


58  PREPARATION    OF   REAGENTS 

the  solution  with  HgCL,,  since  the  sensitiveness  of  the  Nessler 
depends  upon  this  saturation. 

Phenol-Sulphonic  Acid 

32  c.c.  of  concentrated  H.^SO^  are  added  to  4  c.c.  of  pure 
phenol.  These  are  well  mixed  and  heated  to  100°  C.  for  two  or 
three  hours,  no  c.c.  of  distilled  water  are  then  added  and  the 
solution  is  ready  for  use. 

Potassium  Chromate  Solution 

A  strong  solution  of  pure  neutral  KgCrO^  free  from  chlorine  is 
required. 

Dissolve  some  crystals  of  pure  K2Cr04  in  pure  distilled  water, 
and  when  the  solution  is  made,  add  a  drop  or  two  of  the  standard 
solution  of  AgNOg  until  a  permanent  red  precipitate  is  formed. 
This  ensures  the  absence  of  any  chlorine  in  the  solution.  After 
the  precipitate  has  settled,  syphon  or  decant  the  clear  yellow  fluid 
into  a  small  clean  bottle. 

Potassium  Ferrocyanide  Solution 

I  gramme  of  K4Fe(CN)^  is  dissolved  in  100  c.c.  of  distilled 
water. 

Potassium  Iodide  Solution 

This  solution  should  be  made  as  it  is  required,  by  adding 
a  crystal  of  KI  into  a  test-tube,  and  half  filling  it  with  distilled 
water. 

Before  being  used,  a  little  starch  solution  should  be  added 
to  a  few  drops  diluted  with  water,  in  order  to  ensure  the  absence 
of  free  iodine. 

A  solution  of  zinc  iodide  is  frequently  used  instead  of 
potassium  iodide,  since  the  former  does  not  liberate  free  iodine 
on  keeping,  as  does  the  latter. 

Starch  Solution 

This  solution  must  be  made  up  on  each  occasion  as  it  is 
required. 

As  much  starch  as  will  go  on  to  an  ordinary  bacteriological 
platinum  loop  is  dropped  into  a  clean  test-tube,  and  the  test- 
tube  is  three-parts  filled  with  distilled  water  and  well  shaken. 
It  is  then  well  boiled  until  the  liquid  becomes  quite  clear,  and 
allowed  to  cool,  when  it  is  ready  for  use. 


STANDARD   SOLUTIONS  59 

Sodium  Thiosulphate  Solution 

Dissolve  2  grammes  of  the  thiosulphate  in  1000  c.c.  of  distilled 
water. 

The  solution  undergoes  changes  and  becomes  weaker,  so  that 
in  practice  it  is  standardized  every  time  it  is  used,  by  making 
control  or  blank  experiments  side  by  side  with  the  sample. 

Sulphuretted  Hydrogen  Water 

This  is  made  by  acting  on  FeS  with  dilute  HCl,  passing  the 
gas  through  a  small  quantity  of  water,  and  then  into  distilled 
water  until  no  more  HgS  is  dissolved  by  the  water. 

The  HgS  solution  must  be  kept  in  a  well-stoppered  bottle,  and 
preferably  in  the  dark. 

STANDARD    SOLUTIONS 

Gefieral  Considerations.  Standard  solutions  are  made  to  contain 
either  a  known  or  definite  amount  of  a  substance  in  a  certain 
measure,  or  an  amount  sufficient  to  neutralize  or  precipitate  a 
definite  weight  of  another  substance.  Thus  the  standard 
ammonia  is  a  solution  of  ammonium  chloride  of  such  a  strength 
that  each  c.c.  contains  o'ooi  gramme  of  ammonia.  The  standard 
silver  nitrate,  on  the  other  hand,  contains  that  amount  of  silver 
nitrate  in  each  c.c.  which  exactly  precipitates  o'ooi  gramme  of 
chlorine. 

In  making  the  standard  NH^Cl  solution  we  require  i  gramme 

of   NH3  per   litre.     The    combining   weight   of  the    former   is 

53'5 
5 3 "5,  and  of  the  latter  17.     We  require,  therefore, grammes 

(i.e.  3"i47  grammes)  of  NH^Cl  in  a  litre. 

In  a  similar   manner  we   require  sufficient  AgNO^  dissolved 

in  a  litre  of  water  to  precipitate   i  gramme  of  CI.     The  c.w.  of 

AgNO;^  is   1697,  and  that  of  CI  35 '5.     The  amount  of  AgNOg 

169*7 
necessary  IS  therefore    - — :—   grammes;  i.e.  4*780.     Thus  it  re- 

mains  to  weigh  4*780  grammes  of  AgNOg  and  dissolve  them  in 
I  litre  of  water. 

The  labour  involved  in  weighing  out  exactly  3*147  or  4*780 
grammes  is,  for  those  who  are  not  very  adept  at  balance  work,  very 
great,  and  a  simpler  method  is  to  weigh  out  a  certain  quantity 
exactly  and  to  calculate  the  amount  of  water  required. 


6o  STANDARD   SOLUTIONS 

Great  accuracy  can  be  obtained  in  measuring  water  with 
graduated  flasks  and  pipettes.  For  instance,  if  970  c.c.  was 
the  quantity  required,  a  1000  c.c.  flask  would  be  filled  to  the 
graduation  mark,  and  20  c.c.  and  10  c.c.  could  be  removed 
with  pipettes  graduated  for  these  quantities.  If  1270  c.c.  were 
required,  1000  c.c.  and  250  c.c.  flasks  could  be  filled  and  drained 
well  into  one  holding  1500  or  2000  c.c.  and  20  c.c.  added  by 
means  of  a  20  c.c.  pipette. 

All  standard  solutions  should,  of  course,  be  always  kept  in 
glass-stoppered  bottles. 

Standard  Ammonium  Chloride 

NH4CI,  m.w.  53*5;  NH3,  m.w.  17 

A.  Strong  Solution 

Weigh  out  as  nearly  as  possible  3*15  grammes  of  dry  anhydrous 

NH.Cl  and  dissolve  it  ui  x  i    litre    of  distilled    ammonia- 

3-15 

free  water.  xtit 

I  c.c.  =o"ooi  gramme  NH3 

B.    Weak  Solution 

Measure  10  c.c.  of  "  A"  very  accurately  by  means  of  a  10  c.c. 
pipette,  and  add  990  c.c.  of  distilled  ammonia-free  water. 

I  c.c.  =o'ooooi  gramme  NH3 

Standard  Calcium 

Each  c.c.  of  the  standard  must  contain  an  amount  of  CaCl2 
having  the  same  weight  of  Ca  as  o"ooi  gramme  of  CaC03. 

Weigh  as  nearly  i  gramme  of  pure  crystalline  calcite  as  possible, 

and  dissolve  it  in  the  least  quantity  of  dilute  HCl  which  will 

dissolve  it,  taking  care  to  cover  the  vessel  in  which  the  solution  is 

being  made  with  a  watch  or  clock  glass  to  prevent  the  loss  of 

calcium  by  the  spitting.     Evaporate  to  dryness  over  a  water  bath, 

dissolve  again  in  water,  and  evaporate  to  dryness  a  second  time ; 

in  order  to  ensure  the  absence  of  HCl  it  is  advisable  to  repeat 

this  a  third  time.    Now  dissolve  the  CaClg  in  the  proper  quantity 

w 
of  freshly  boiled  distilled  water,  i.e. —   x  1000  c.c.  where  iv  is  the 

weight  of  CaCOg  taken. 


STANDARD    SOLUTIONS  6i 

Standard  Copper  Solution  ^ 

CuSO^*  5H2O,  m.w.  249  ;  Cu,  c.w.  63 

I  gramme  of  copper  is  contained  in  3 "95  grammes  of  copper 
sulphate.     Weigh  out  as  nearly  as  possible  3*95  grammes  of  the 

crystals  of  CuSO^,  and  dissolve  them  in  —^ —  x  1000   c.c.  of  dis- 
tilled water.  J  cc.^o-ooi  gramCu 

Standard  Indigo  Solution 

Weigh  out  approximately  2  grammes  of  indigo  carmine.  Digest 
this  with  10  grammes  of  Nordhausen  sulphuric  acid  for  24 
hours.  Add  30  c.c.  of  concentrated  sulphuric  acid  and  mix  well. 
Pour  this  carefully  into  about  500  c.c.  of  distilled  nitrate-free 
water.  Wash  the  indigo  out  of  the  vessel  with  distilled  water, 
a  few  c.c.  at  a  time,  until  all  the  indigo  has  disappeared.  Filter 
and  make  up  the  solution  to  i  litre. 

In  order  to  standardize  the  indigo  solution,  a  burette  graduated 
in  ~\.\\  c.c.  is  filled  with  the  solution.  2  c.c.  of  the  standard 
nitrate  solution  are  mixed  with  18  c.c.  of  distilled  water  and 
poured  into  a  small  wide-mouthed  flask.  20  c.c.  of  strong  HoSO^ 
are  quickly  run  into  the  flask  and  well  mixed.  The  indigo  is 
now  run  in,  a  few  drops  at  a  time,  and  the  flask  well  shaken. 
After  a  certain  quantity  of  indigo  has  been  run  in,  the  greenish 
colour,  which  quickly  disappeared  at  first,  becomes  permanent. 
The  amount  of  indigo  required  is  next  read  off.  Suppose  the 
quantity  required  was  found  to  be  2*2  c.c. 

Then  2 '2  c.c.  of  indigo  =  2  c.c.  of  standard  nitrate;  but 
I  c.c.  of  nitrate  =  o'ooooi4  gramme  of  nitrogen 

I  c.c.  of  indigo  =  -7-     of    0*000014  x  2     grammes    of 

nitrogen        =0-0000127  gramme 

Several  experiments  must  be  made  to  ensure  the  correctness  of 
these  figures,  and  when  the  true  figures  have  been  found,  the 
indigo  should  be  labelled 

"  I  c.c.  =o"ooooi2  7  gramme  N  " 

^  The  standard  solutions  of  lead,  copper,  and  iron  are  made  up  so  that 
I  c.c.  =0*001  gramme.  When  using  it  is  convenient  to  dilute  at  least  ten 
times. 


62  STANDARD   SOLUTIONS 

Standard  Iron  Solution 

A. 

FeSO^ .  7H2O,  m.w.  278  ;  Fe,  c.w.  56 
I  gramme  of  iron  is  contained  in  4"96  grammes  of  ferrous  sul- 
phate.    Weigh  out  as  nearly  as  possible  4*96   grammes   of  the 

w 
crystals  of  pure  FeSO^,  and  dissolve  them  in  -7-7  X  1000    c.c.     of 

distilled  water.  j  c.c  =  o-ooi  gramme  Fe 

B. 
(NH,)oFe2(SOJ^.6H,0,  m.iv.  640 
Owing  to  the  fact  that  absolutely  pure  FeSO^  is  difficult  to 
procure,    it    is    better    to    make   up    a    standard    solution    with 
ammonium  iron  alum,  which  has  the  advantage  that  it  is  stable. 

I  gramme  of  iron  is  contained  in  5714  grammes  of  ammonium 
iron  alum. 

Weigh  out   as  nearly  as  possible  this  quantity  and  dissolve 

.    .        w  .    . 

it  in  X  1000  c.c.  of  distilled  water. 

5714 

I  c.c.  =  00001  gramme  Fe 

Standard  Lead  Solution 

Pb(C2H302)o .  3H2O,  m.w.  378*4;  Pb  c.w.  2064 
I  gramme  of  lead  is  contained  in  i'83  grammes  of  lead  acetate. 
Weigh  out  as  nearly  as  possible  1*83  grammes  of  pure  lead  acetate 
and   add  it  to  about  500  c.c.  of  distilled  water,  and  then  add 
sufficient  acetic  acid  to  render  the  solution  clear. 

IV 

Add  water  to  make  up  the  quantity  to  — 7^-  x  1000  c.c. 
I  c.c.  =  o*ooi  gramme  Pb 

Standard  Nitrate  Solution 

KNOo,  771.W.  =  loiT  ;  N,  C.2V.  =  14 

Weigh   out  as  nearly  as  possible  I'oii   grammes  of  KNO3. 

.    .       w  .    . 

Dissolve  this  in x  1000   c.c.  of  distilled  water.     Each  c.c. 

lOI  I 

of  the  solution  will  contain  0001  gramme  of  KNO3,  ^^  be  equiva- 
lent to  0*000014  gramme  of  N. 


STANDARD   SOLUTIONS  63 

Standard  Nitrite  Solution 

AgNOo,  m.w.  1537  ;  Ag,  c.w.  1077 

Weigh  out  as  nearly  as  possible  0-406  gramme  of  pure  silver 
nitrite.  Dissolve  it  in  boiling  distilled  water,  and  add  sufficient 
sodium  chloride  to  precipitate  the  whole  of  the  silver.     Make  the 

solution  up  to    7  of  1000  c.c.  with  distilled  water,  and  allow 

^        0.406 

the   silver   chloride   to  settle.     Remove    100   c.c.   of  the  clear 

solution  and  dilute  it  to  i  litre  with  distilled  water. 

I  c.c.  =0*0000 1  gramme  NOg 

Standard  Potassium  Permanganate  Solution 

KMnO^,  vi.iv.  316  ;  Oo,  m.w.  32 

K.MnoOs  +  3H2SO^  =  2MnS0^  +  3H0O  +  5O 

i.e.  316  grammes  of  KMnO^  yield  80  grammes  of  oxygen.     The 

solution  has  been  found  most  convenient  when  10  c.c.  of  it  yield 

o'ooi  gramme  of  Oo-     i  litre  of  the  solution   must  contain   o'l 

gramme    of  available    oxygen.     The   amount    of   permanganate 

.    .     316 
required  to  allow  this  is  -o—  x  01  grammes  in  a  litre  ;  i.e.  0*395 

gramme.     Weigh  out  therefore  as  nearly  as  possible  0*395  gramme 
of  pure  potassium  permanganate  and  dissolve  it  in    .^      x  1 000  c.c. 

of  pure  distilled  water  {iv  being  the  weight  of  the  permanganate 
actually  taken).     The  solution  is  then  to  be  labelled 

"  10  c.c.  =  O'OOI  gramme  Oo" 

Standard  Silver  Nitrate 

AgNO.  +  NaCl  =  AgCl  +  NaNOg 
1077  +  14  +  48  grammes  of  AgNOg  are  required  to  precipitate 

169*7   /.  \  f 

35*5  grammes  of  CI.     Therefore-^;—: — (i.e.    4*780)    grammes    ot 

35'5 
AgNOg  will  be  necessary  to  precipitate  i  gramme  of  CI. 

As  the  solution  must  contain  enough  silver  nitrate  in  each  c.c. 

to  precipitate  o'ooi  gramme  of  CI,  it  is  evident  that  every  litre 

should  contain  4*780  grammes  of  the  nitrate. 


64  STANDARD    SOLUTIONS 

Weigh  out  accurately,  as  nearly  as  possible  4.780  grammes  of 
pure  recrystallized  silver  nitrate.  Dissolve  in  about  500  c.c.  of 
water  in  a  perfectly  clean  chlorine-free  flask  ;  add  more  distilled 

w 

water,    so  that    the  total  bulk   of  the  water  shall  equal    ^ 

'  ^         4*780 

X  1000    c.c.   where  lu   is  the  actual    weight  taken.     When  the 

dilution   is    completed   the   solution   should    be   poured   into    a 

suitable  glass-stoppered  bottle  and  kept  in  the  dark. 

Suppose  that  tv  was  found  to  be  5 '124  grammes,  then  the  total 

must  be  ^ ^  of  1000  c.c.  =  107 1'o  c.c. 

4-780 

Standard  Soap  Solution 

Each  c.c.  of  the  soap  solution  must  contain  an  amount  of  soap 
which  will  precipitate  o"ooi  gramme  of  CaCOg. 

Weigh  out  10  grammes  of  sodium  oleate  or  the  Sapo  durus  of 
the  B.P.  and  mix  it  with  a  litre  of  equal  parts  of  methylated 
spirit  and  water. ^ 

Shake  well  from  time  to  time  and  set  aside  in  a  cool  place  for 
24  hours.  Filter  into  a  flask  which  has  been  thoroughly  well 
washed  out  with  distilled  water. 

In  order  to  standardize  the  soap,  it  is  necessary  in  the  first 
place  to  find  the  amount  of  the  soap  which  is  required  to  make 
a  permanent  lather  with  50  c.c.  of  distilled  water.  Suppose  this 
is  o"6  c.c. 

Into  a  6-oz.  bottle  run  6  c.c.  of  the  standard  calcium  solution, 
and  add  44  c.c.  of  distilled  water.  Now  find  the  quantity  of  the 
soap  which  is  required  to  form  a  lather.  Suppose  that  5*3  c.c. 
are  necessary.     Then  we  have — 

Soap  for  o"oo6  gramme  CaCOg-h  50  c.c.  water  =  5 '3  c.c. 
,,        50  c.c.  water  .         .         .         .  =  o"6c.c. 

„        o*oo6  gramme  CaCOg       .         .         .=47  c.c. 

But  the  soap  must  be  of  such  a  strength  that  6  c.c.  are 
required.     Therefore  the  volume  of  the  standardized  soap  must 

6  .    . 

be  —7  of  what  it  is  unstandardized.     Suppose  that  in  this  case 

the  volume  is  940  c.c.     Then  the  total  volume  must  be  —    of 

47 

^  For  the  solution  and  subsequent  dilution,  exactly  equal  parts  of  methylated 
spirit  and  water  should  be  mixed  together  and  allowed  to  cool.  The  quantities 
of  the  cold  mixture  should  be  measured. 


STANDARD   SOLUTIONS  65 

940  c.c.  =  1200  c.c.  That  means  that  260  c.c.  of  spirit  and 
water  must  be  added  so  that  i  c.c.  of  the  soap  shall  exactly 
precipitate  i  c.c.  of  the  standard  calcium  solution. 

Standard  Thiosulphate  Solution 

Na2S.203*5H20,  vuw.  248 

This  solution  is  made  so  that  i  c.c.  =  0*00025  gramme  of  oxygen. 
On  referring  to  Winkler's  method  for  estimating  the  oxygen 
dissolved  in  water  it  is  seen  that,  according  to  the  equations, 
16  grammes  of  oxygen  will  liberate  254  grammes  of  iodine. 

On  referring  to  the  oxygen  absorbed  process  it  will  be  seen 
that  thiosulphate  takes  up  iodine,  thus 

2NaoS203  +  lo  =  2NaI  +  Na^S^^ 

that  is,  316  grammes  of  thiosulphate  combine  with  254  of  iodine. 

Thus    since  16  grammes  O  liberate  254  grammes    I,   and    254 

grammes  I  are  converted  into  Nal  by  316  grammes  of  NaoS203, 

16  grammes  O  are  equivalent  to  316  grammes  NaoS^Og. 

Na2S20.j  has  5  molecules  of  water  of  crystallization  ; 

.".  316  grammes  Na2S^03  =  496  grammes  Na2S203 '  5H2O 

.    0*00025 
I   c.c.  of  our  standard  solution  must  therefore  contaui  -^ — 

of  ^()6  grammes  of  thiosulphate,  i.e.  0*00775  ;  or  in  other  words, 
7 '7 5  grammes  of  crystalline  sodium  thiosulphate  are  dissolved  in 
I  Htre  of  water. 


ANALYSIS   OF   MILK 

Cow's    milk    contains   proteins,    carbohydrates,    fats,    salts    and 
water. 

The  average  composition  is  : — 
Water  87-2% 


Solids  1 2  "8%,  consisting  of 


'  Sugar,  4 -8% 
.    Fat,  3-7% 

Protems,  3'6% 
I  Ash,  o-7% 

Cow's  milk,  from  the  point  of  view  of  the  hygienist,  is  the 
only  kind  of  any  importance.  The  results  of  a  large  number  of 
analyses  have  shown  that  the  milk  of  a  healthy  cow  contains 
certain  proportions  of  the  various  constituents.     Although  the 

5 


66  ANALYSIS    OF    MILK 

composition  varies  with  the  time  of  year,  the  breed  of  the  cow, 
the  interval  since  calving,  the  lactation  after  first  or  subsequent 
parturition,  etc.,  it  has  been  found  that  no  milk  from  a  healthy 
cow  is  worse  than  a  certain  standard.  If,  therefore,  a  sample  of 
milk  is  examined  and  found  to  fall  below  this  standard,  in  some 
manner  or  other,  the  conclusion  is  arrived  at  that  cream  has  been 
extracted,  water  added,  etc. 

It  is  therefore  necessary  to  know  what  these  standards  are,  in 
order  to  be  able  to  say  whether  the  sample  of  milk  under  exami- 
nation is  normal  or  no. 

The  determinations  upon  which  the  quality  of  the  milk  is 
decided  are : — 

I.  The  specific  gravity.  2.  The  total  solids.  3.  The  fat. 
4.  The  total  solids  not  fat.  5.  The  total  ash,  6.  The  quality 
of  the  ash. 

THE  SPECIFIC   GRAVITY 

Apparatus  required 

1.  A  specific  gravity  bottle. 

2.  A  good  balance  (sensitive  to  o"ooi  gramme). 

The  Process 

1.  A  specific  gravity  bottle  holding  25  c.c.  is  thoroughly  cleaned 

with  strong  HCl  and  washed  with  hot  water.  It  is  then 
dried  outside,  and  rinsed  with  alcohol  and  finally  with  ether. 
The  ether  is  expelled  by  blowing  into  the  bottle  with  the 
nozzle  of  a  blow-pipe. 

The  perforated  stopper  should  be  treated  in  the  same 
way. 

2.  About  50  c.c.  of  the  milk  and  a  like  quantity  of  distilled  water 

should  be  allowed  to  stand  in  glass-stoppered  bottles  in  the 
laboratory  for  an  hour  or  so,  in  order  that  the  temperature  of 
each  may  be  that  of  the  laboratory. 

3.  The   bottle  is  carefully  weighed   with  the   stopper   and   the 

weight  noted. 

4.  The  specific  gravity  bottle  is  now  filled  with  the  water  to  the 

top  of  the  neck.  The  stopper  is  then  carefully  inserted  so 
that  no  bubbles  of  air  are  contained,  and  the  water  fills  the 
hole  in  the  stopper.  The  bottle  is  carefully  dried  outside 
with  a  towel,  care  being  taken  not  to  heat  the  bottle  with 
the  hand  in  the  operation. 


THE   TOTAL   SOLIDS  67 

5.  The  bottle  containing  the   water   is    now  weighed   and   the 

weight  noted. 

6.  The  bottle  is  next  emptied,  dried,  and  filled  with  the  milk, 

taking  all  the  precautions  as  before. 

7.  It  is  again  weighed,  with  the  milk,  and  the  weight  noted. 


EXAIN 

^PLE 

Weight  of  bottle 

„              „      +  water 

•   18-306  grammes 

43 '3  H  grammes 

Weight  of  water  . 

25-008  grammes 

Weight  of  bottle  +  milk 

44*056  grammes 

Weight  of  milk 

25750  grammes 

Sp.  gr.  of  milk  = 

25750 
=    ^  ^„  X  1000 
25*008 

=  1029-6 

Notes 

It  will  be  observed  that  the  temperature  of  both  water  and 
milk  is  that  of  the  laboratory.  This  is,  of  course,  not  the 
theoretical  manner  of  taking  the  specific  gravity,  but  it  is  done 
in  practice,  and  the  error  is  very  small.  If  it  were  called  the 
relative  density  instead  of  the  specific  gravity,  perhaps  no  objec- 
tion could  be  raised  either  to  the  method  or  title. 

A  simpler  method  is  to  take  the  sp.  gr.  with  a  lactometer,  or 
hydrometer,  but  this  is  rarely  done  by  analysts  of  repute,  as  the 
error  is  greater  than  that  obtained  by  weighing,  owing  to  a  variety 
of  circumstances,  including  the  temperature,  the  inaccuracy  of 
the  instrument,  etc. 

Before  taking  the  sp.  gr.  the  milk  must  be  well  shaken,  so  as 
to  obtain  a  fair  sample.  This  statement  applies  to  all  the  other 
determinations. 

THE  TOTAL   SOLIDS 

This  determination,  as  in  the  case  of  water,  aims  at  finding 
the  percentage  of  solid  constituents  in  the  liquid,  by  evaporating 
the  milk  and  weighing  the  residue  left. 


6^  ANALYSIS   OF   MILK 

The  Process 

1.  Having  thoroughly  cleaned  and  dried  a  platinum  dish,  weigh  it. 

2.  Weigh  out  in  the  tared  dish  5  grammes  of  the  milk  after  well 

shaking  it. 

3.  Evaporate  to  dryness  over  a  water  bath^  inverting   a   glass 

funnel  over  the  dish  to  prevent  any  dust  from  getting  into 
the  dish.     The  drying  takes  about  two  hours. 

4.  Heat  in  the  water  oven  for  half  an  hour,  and  weigh  the  dish 

after  it  is  cooled. 

5.  Replace  in  the  oven  for  a  further  interval  and  again  weigh. 

If  there  is  no  decrease  in  the  weight,  this  is  accepted.  If 
there  is  a  decrease,  the  dish  is  placed  in  the  oven  again  for 
a  short  time  and  again  weighed,  until  two  successive  weigh- 
ings give  no  difference. 

EXAMPLE 

Platinum  dish         .         .         .      =  io"324  grammes 
„  „    +milk        .         .      =15-324      „ 

„  „    +  solids     .         .      =10-964      „ 

Total  solids  .         .         .      =  10*964-10*324  grammes 

=   0*64  gramme 
But  this  is  the  quantity  in  5  grammes ; 

.'.  total  solids  %  .  .  .         .      =0*64x20 

Notes  ='^-«°/° 

The  skin  that  forms  on  the  surface  of  the  milk  delays  the 
drying.  The  formation  of  this  skin  may  be  prevented,  and  the 
process  therefore  hastened,  by  the  addition  to  the  milk,  before 
evaporation,  of  a  few  drops  of  a  mixture  of  one  part  of  acetic 
acid  with  nine  of  methylated  spirits. 

In  order  to  weigh  out  exactly  5  grammes  of  milk,  the  dish  is 
tared  and  5  grammes  are  added  to  the  weights  already  counter- 
poising the  dish.  Now  pipette  the  milk  in  a  5  c.c.  pipette  and 
allow  4*7  c.c.  to  run  into  the  dish  on  the  scale  of  the  balance, 
taking  care  to  have  the  balance  down.  Allow  the  milk  to  run 
into  the  dish  after  this  drop  by  drop,  until  upon  raising 
the  beam  it  is  found  that  there  is  just  too  much  milk.  With 
a  clean,  small-pointed,  glass  rod  remove  a  trace  of  the  milk  and 
again  weigh.  Wipe  the  rod  on  a  clean  towel  and  continue  to 
remove  traces  until  the  milk  weighs  exactly  5  grammes.  A  little 
practice  will  enable  the  experimenter  to  perform  the  weighing 
both  quickly  and  accurately. 


THE   FAT  69 

THE  ASH 

Having  weighed  the  total  solids,  the  dish  is  heated  to  dull  red- 
ness over  a  Bunsen,  or  preferably  over  an  Argand  burner,  until 
the  whole  of  the  organic  matter  is  burnt. 

The  process  is  expedited  by  breaking  up  the  masses  of  dried 
milk  with  a  somewhat  stiff  platinum  wire  from  time  to  time. 

When  the  whole  of  the  contents  are  of  a  greyish  white  appear- 
ance, the  dish  is  removed  to  a  desiccator  to  cool  and  afterwards 
weighed. 

EXAMPLE 
Weight  of  dish       ....      =  1 0*3 24  grammes 
„  „      -1-ash     .         .         .      =10-358      „ 


Ash  .....      =r   0*034  gramme 

But  this  is  the  ash  from  5  grammes  of  milk ; 

.'.  the  percentage  of  ash  =  0*034  x  20 

=  o-68% 

.       THE  FAT 

Apparatus  required 

1.  A  Schmidt- Werner  tube. 

2.  A  stout  test-tube,  carrying  a  wash-bottle  arrangement. 

3.  A  platinum  dish. 

4.  A  20  c.c.  pipette. 

The  Process 

1.  10  grammes  of  milk  are  quickly  and  accurately  weighed  into 

the  platinum  dish. 

2.  The  Schmidt-Werner  tube  is  clamped  in  a  vertical  position, 

after  having  been  thoroughly  cleaned  and  drained ;  and  a 
small  funnel  (cut  short  as  to  its  tube)  is  placed  in  the  mouth 
of  the  tube. 

3.  The  milk  is  poured  down  the  funnel,  the  remains  of  the  milk 

are  then  washed  on  to  the  funnel  from  the  dish  with  the 
strong  HCl  (which  must  be  pure)  as  contained  in  the 
extemporized  wash-bottle.  The  milk  is  then  washed  out  of 
the  funnel  with  the  acid,  and  finally  the  sides  of  the  tube 
are  washed  down  with  the  acid,  and  sufficient  acid  added 
so  that  the  mixture  of  milk  and  acid  reaches  the  20  c.c 
mark. 


70  ANALYSIS   OF   MILK 

4.  The  tube  is  shaken  so  as  to  mix  the  milk  and  acid  well,  and 

the  milk  is  then  boiled,  the  tube  being  constantly  shaken. 
When  the  liquid  is  of  a  fairly  deep  brown  colour,  the  heat- 
ing is  stopped. 

5.  The  whole  is  then  allowed  to  cool,  by  immersing  the  tube  in 

water  if  desired. 

6.  When  the  whole  is  cool,  ether  is  poured  in  to  the  50  c.c. 

mark.  A  cork  is  now  inserted  into  the  mouth,  and  the  tube 
inverted  gradually  so  that  the  whole  of  the  brown  liquid 
collects  in  the  upper  end  of  the  tube. 

This  must  be  repeated  fifteen  or  twenty  times,  so  that  the 
ether  may  come  into  contact  with,  and  take  up  all  the  fat. 
The  tube  is  then  held  vertically  and  rotated  quickly  between 
the  hands  in  order  to  get  the  debris  to  settle  well,  so  that 
the  level  of  the  ether  can  be  easily  read. 

7.  A  20  c.c.  pipette  having  indiarubber  tubing  at  the  upper  end 

is  now  inserted  into  the  tube,  and  exactly  20  c.c.  of  the 
ether  are  sucked  out  of  the  tube.  The  ether  can  be  easily 
held  in  the  pipette  by  pinching  the  indiarubber  tubing. 

8.  The  20  c.c.  of  ether  are  then  allowed  to  run  into  a  clean 

platinum  dish,  which  is  then  placed  in  a  water  oven,  at 
60°  C,  in  order  to  drive  off  the  ether. 

9.  When  the  ether  is  completely  evaporated,  the  dish  now  con- 

taining the  fat  is  weighed. 
I  o.  The  ether  left  in  the  tube  is  read  off  and  noted  for  the  subse- 
quent calculation. 

Explanation 

The  fat  in  the  milk  being  in  the  form  of  a  perfect  emulsion 
cannot  be  taken  up  by  ether  without  previous  treatment.  Boiling 
with  HCl  converts  the  albuminous  envelopes  round  the  fat  into 
soluble  acid-albumin,  the  fat  is  set  free  and  rises  to  the  top.  The 
ether  is  now  able  to  dissolve  it. 


EXAMPLE 
Weight  of  milk  taken 

„  dish 

„  dish  +  fat 

„  fat  . 

Ether  left  in  tube 


=  lo'ooo  grammes 
=  42312        „ 
=  42-638 

=    0*32  6  gramme 
=    3"5  c.c. 


Total  fat=  -^  X  o '3  2  6  gramme  (since 
20 

0*326  gramme  of  fat  was  present  in 

20  c.c.  of  ether)    .         .         .         .      =   0*383  gramme 


ADULTERATION    OF   MILK  71 

But  this  quantity  is  present  in  10  grammes  of  milk ; 
.*.   100  grammes  contain  3'83  grammes;  or  the  milk  contains 
3-83%  of  fat. 

Notes 

The  Werner-Schmidt  tube  is  fixed  vertically  to  prevent  the 
milk  from  getting  into  the  upper  bulb,  and  a  funnel  is  used  to 
the  same  end. 

If  several  estimations  are  to  be  made,  the  20  c.c.  pipette 
should  not  be  cleaned  out,  but  the  ether  must  be  drained  each 
time  into  the  platinum  dish. 

After  having  done  this,  it  will  be  noticed  that  there  is  a  modi- 
cum of  fat  lining  the  pipette  and  this  amount  is  constant.  From 
this  it  is  evident  that  the  first  estimation  done  with  a  new  or 
clean  pipette  will  be  slightly  under  the  proper  figure. 

In  mixing  the  ether  with  the  fat,  HCl,  etc.,  care  must  be  taken 
not  to  shake  the  tube  whilst  the  brown  sediment  and  ether  are 
mixed  together.  If  it  is  done,  a  froth  will  be  formed  which  is 
difficult  to  get  rid  of. 

When  all  the  ether  is  at  one  end,  that  end  should  be  well  shaken, 
in  order  to  get  the  ether  well  in  contact  with  the  walls  of  the  tube. 

ADULTERATION    OF   MILK 

When  a  milk  vendor  finds  that  the  consumption  of  milk 
exceeds  the  production,  there  are  certain  courses  open  to  him. 
Firstly,  he  may  refuse  to  supply  some  of  his  customers ;  secondly, 
he  may  increase  the  production;  thirdly,  he  may  make  the 
production  fit  the  consumption.  The  last  course  is  not  altogether 
unknown ;  and,  in  order  to  follow  it,  the  dishonest  vendor  adds 
water  to  the  milk.  Sometimes  he  wishes  to  sell  cream,  and  then 
he  may  deplete  some  of  his  milk  of  fat,  and  sell  the  resulting 
skimmed  milk  as  genuine. 

If  he  abstracts  cream  he  will  raise  the  specific  gravity  of  the 
milk ;  if  he  adds  water  he  will  lower  it.  It  may  possibly  occur 
to  him  that  some  of  his  customers  have  lactometers ;  and  so, 
judiciously,  he  abstracts  cream  and  adds  water.  If  these  opera- 
tions are  carefully  performed,  the  resulting  product  will  have  a 
normal  specific  gravity ;  and  the  dishonest  milkman  may  trade 
unsuspected,  until  an  inclement  fortune  sends  some  of  his  milk 
to  an  analyst.  Such  frauds  in  connection  with  milk  are  often 
referred  to  by  the  kindly  name  of  sophistication. 


72  ANALYSIS    OF    MILK 

Standards  for  Milk 

In  order  to  detect  a  fraudulent  milk  vendor,  it  is  necessary  to 
have  a  standard  to  which  milk  should  conform ;  if  the  milk  fails 
to  come  up  to  the  standard,  then  it  can  be  said  not  to  be 
genuine. 

It  has  been  ascertained  that  milk,  if  genuine,  should  contain  : — 

1.  At  least  3%  of  fat. 

2.  At  least  8-5%  of  solids  not  fat. 

And  that  skimmed  milk,  if  unwatered  and  genuine,  should  con- 
tain at  least  9'o%  of  solids  not  fat. 

These  are  legal  standards ;  and  if  a  milk  sample  fails  to  attain 
to  these  it  is  considered  to  be  adulterated  and  not  genuine. 

Addition  of  Water 

When  water  is  added  to  milk  the  specific  gravity  of  the  sample 
is  lowered,  and  the  solids  both  fatty  and  non-fatty  are  diminished. 
The  amount  of  water  added  is  determined  from  the  amount  of 
solids  not  fat.  Thus  a  sample  of  milk  was  found  to  contain  8% 
of  solids  not  fat;  but  8*5%  of  solids  not  fat  denotes   100%  of 

genuine  milk.     Therefore  8%  of  solids  not  fat  denotes  — ^ 

=  94"i%  of  genuine  milk  ;  or,  in  other  words,  about  6%  of  water 
has  been  added  to  the  milk. 

Again,  the  amount  of  water  added  may  be  calculated  from  the 
ash.  The  ash  in  milk  is  fairly  constant  at  o"7%,  although  there 
is  no  legal  standard  for  it.  A  milk  sample  was  found  to  give 
o*6%  of  ash  :  now  07%  of  ash  shows  100%  of  pure  milk  ;  there- 
fore o*6%   of  ash   shows    =  85-7%  of  pure  milk.      So 

07 

about  15%  of  water  has  been  added  to  this  sample. 

In  legal  work  and  ordinary  routine  work,  however,  it  is 
more  convenient  to  calculate  the  added  water  from  the  figure 
for  solids  not  fat,  as  has  been  shown  above. 

Abstraction  of  Cream 

Removal  of  cream  raises  the  specific  gravity  of  milk,  and  lowers 
the  amount  of  fat  present.  The  amount  of  cream  abstracted  is 
measured  by  the  estimation  of  the  fat. 

Thus  a  sample  of  milk  was  found  to  have  only  2*5%  of  fat. 


ADULTERATION    OF    MILK  73 

Now  3%  of  fat  show  that  the  fat  in  the  milk  is  all  present ;  or  a 

2 '  c  X  1 00 
figure  of  3  denotes  100%  of  fat.    Therefore  2*5  denotes  —5 

=  83*3%  of  fat  originally  present.  So  more  than  16%  of  the 
original  fat  has  been  abstracted. 

Where  the  fat  is  low  and  the  solids  not  fat  are  average,  it  may 
be  inferred  that  the  diminished  fat  figure  is  due  to  the  abstraction 
of  cream  and  not  to  the  addition  of  water.  Where  the  fat  is 
much  reduced,  and  the  solids  not  fat  slightly  reduced,  it  may  be 
inferred  that  cream  has  been  abstracted  and  water  added. 

Rarely  condensed  milk  is  added  to  skimmed  or  watered  milk 
in  order  to  supply  the  deficiency  in  fat.  The  fraud  is  detected 
by  the  abnormally  high  figure  for  total  solids,  and  by  the 
increase  in  sugar.  Condensed  milk  contains  much  sugar  and 
solids — sometimes  as  much  as  40%. 

Note 

It  has  been  found  that  the  specific  gravity,  total  solids,  and  fat 
bear  a  somewhat  constant  relation  to  one  another.  Advantage 
has  been  taken  of  this  fact,  and  a  formula  has  been  calculated  for 
deducing  the  fat  from  the  specific  gravity  and  total  solids.  This 
is  a  great  advantage  when  many  samples  of  milk  have  to  be 
estimated ;  because  the  estimation  of  the  fat  requires  more 
attention  than  that  of  the  total  solids. 

The  formula  is  : — 

_  ^      Spec.  Grav. — 1000  ,  .     6F 

T.S.  =  -^- +  0-14  + 

4  5 

Where  T.S.  =  Total  solids,  and  F  =  fat. 

EXAMPLE 

A  milk  sample  had  a  specific  gravity  of  1032,  and  had 
1 2 '34%  of  total  solids.     Then  : — 

10^2  —  1000  ,  .     6F 

i2'34  =  — ^ -fo-i4+  — 

4  5 

.*.  F  =  3-5. 

Preservatives 

The  most  common  additions  to  milk  are  sodium  carbonate  or 
bicarbonate,  boric  acid  or  borax,  formalin,  and  occasionally 
salicylic  acid. 


74  ANALYSIS   OF   MILK 


Sodium  Carbonate  or  Bicarbonate 

is  added  in  order  to   neutralize   the  acidity  generated  by  the 
growth  of  micro-organisms,  and  to  delay  the  curdling. 
These  may  be  detected 

1.  By  boiling  the  suspected  milk  for  an  hour.     After  prolonged 

boiling,  normal  milk  has  only  a  faint  tinge,  but  milk  to 
which  either  of  these  salts  has  been  added  assumes  a  fairly 
deep  brown  colour. 

2.  By  the  reaction    on  rosolic   acid.     To   lo  c.c.   of  the  milk 

add  lo  c.c.  of  alcohol  and  a  few  drops  of  a  i%  alcoholic 
solution  of  rosolic  acid. 

Normal  milk  will  show  a  brownish  colour,  whereas  milk  with 
NaHCOy  added  will  turn  the  rosolic  acid  a  rose  colour. 

Boric  Acid  or  Borax 

The  presence  of  these  preservatives  may  be  detected  as 
follows : — 

1.  Evaporate  50  c.c.   of  the  milk,  which   has   been   rendered 

slightly  alkaline,  to  dryness,  and  incinerate. 

2.  Dissolve  in  the  minimum  quantity  of  HCl  and  again  evaporate 

to  dryness. 

3.  Dissolve  the  residue  in  a   small  quantity  of  hot  water  and 

moisten  a  piece  of  turmeric  paper  with  the  solution.  Dry 
the  turmeric  paper. 

If  boric  acid  or  borax  was  present  in  the  milk,  the  dry  turmeric 
paper  will  assume  a  rose  or  cherry-red  colour. 

The  quantitative  estimation  is  a  very  lengthy  and  delicate 
process,  and  beyond  the  scope  of  this  work. 

Salicylic  Acid 
This  acid  may  be  detected  as  follows  : — 

1.  Acidify  about  25  c.c.  of  the  milk  with  HCl  and  filter. 

2.  Shake  up  the  filtrate  well  with  ether  and  decant  it. 

3.  Evaporate   the    ether   and    moisten    the    residue   with   ferric 

chloride. 

The  presence  of  salicylic  acid  is  indicated  by  the  development 
of  a  violet  colour. 


ANALYSIS   OF   BUTTER  75 

Formalin 

The  presence  of  small  quantities  of  formalin  in  milk  may  be 
detected  by  the  method  suggested  by  Hehner. 

If  a  few  c.c.  of  milk  are  poured  into  a  test-tube,  and  a  like 
quantity  of  strong  commercial  sulphuric  acid  is  poured  down  the 
side  of  the  tube  so  that  the  two  do  not  mix  freely  ;  at  the  junction 
of  the  H2SO4  with  the  milk,  a  purple  ring  will  be  formed  which 
becomes  more  extensive  upon  gradually  agitating  the  test-tube. 

Notes 

This  test  is  only  available  for  formalin  in  milk,  since  no  such 
reaction  can  be  obtained  with  pure  formalin.  Pure  H2SO4  also 
gives  no  such  reaction,  so  that  the  commercial  acid  must  be 
employed. 

A  still  better  test  is  as  follows : — 

lo  c.c.  are  placed  in  a  test-tube  and  2  c.c.  of  10%  KOH 
solution  and  i  c.c.  of  a  watery  solution  of  phloroglucinol  are 
added.  If  formalin  is  present  a  pink  colour  will  be  at  once 
produced. 


ANALYSIS   OF   BUTTER 

The  term  "butter"  has  been  defined  in  the  Margarine  Act, 
1887,  to  "mean  the  substances  usually  known  as  butter,  and 
made  exclusively  from  milk  or  cream  or  both,  with  or  without 
salt  or  other  preservatives,  and  with  or  without  the  addition  of 
colouring  matter." 

As  in  the  case  of  milk,  the  composition  of  butter  varies  within 
certain  limits.  An  average  pure  butter  has  the  following  per- 
centage composition  : — 

Fat  ....              .  85-45 

Curd  .....  2*75 

Salt  .....  3'25 

Water  .....  8-55 

but  even  in  genuine  butters  the  fat  may  vary  from  82%  to  87% 
and  the  water  a  corresponding  amount,  and  no  butter  should  be 
condemned  as  being  adulterated  with  water  unless  it  contains 
less  than  80^^  of  fat. 


7^  ANALYSIS   OF   BUTTER 

The  proximate  analysis  of  a  sample  of  butter  may  be  under- 
taken as  follows  : — 

ESTIMATION   OF  WATER 
Apparatus  required 

1.  A  platinum  dish  and  a  piece  of  glass  rod. 

2.  A  water  bath  and  a  water  oven. 

3.  A  good  balance. 

The  Process 

1.  Weigh  about  2   or  3  grammes   of  butter  into  the  clean  dry 

platinum  dish. 

2.  Place  the  dish  on  the  water  bath  and  stir  from  time  to  time 

with  the  glass  rod,  leaving  the  latter  in  the  dish  the  whole 
time. 

3.  When  the  visible  water  has  evaporated,  wash  the  fat  off  the 

rod  with  a  little  ether,   and  place  the  dish  in  the  water 
oven  until  all  the  w^ater  and  ether  have  disappeared. 

4.  Remove  to  a  desiccator  until  the  dish  is  cool,  and  weigh. 

5.  Replace  in   the   oven   for  half  an   hour,  again   place  in   the 

desiccator  and  re-weigh. 
If  the  two  weighings  are  alike  or  very  approximate  the  last 
weighing  may  be  taken  as  the  correct  weight  of  the  dry  butter. 
The  loss  in  weight  of  the  butter  represents  the  water  present. 

EXAMPLE 
Platinum  dish  .  .  .    =  1 0324  grammes 

Weight  of  dish  +  butter  .  .    =13*524        ,, 


Weight  of  butter         .  .    =    3-200        ,, 

Weight  of  dish  +  dried  butter  .    =12-960        ,, 

Loss  in  weight  .  .  .    =    0-564  gramme 

.*.  percentage  of  water  =  *L5_i  x  100=  17-60 

Note 

Unless  the  butter  is  stirred  from  time  to  time  during  the 
process  of  evaporation,  the  melted  butter  floats  on  the  surface  of 
the  water,  and  so  prevents  its  evaporation. 

Care  must  of  course  be  taken  to  wash  all  the  fat  off  the  glass 
stirring  rod. 


ESTIMATION   OF   SALT  JJ 

ESTIMATION   OF  SALT 
Apparatus  required 

1.  A  separating  funnel. 

2.  The  apparatus  for  estimating  chlorine  in  water. 

The  Process 

1.  Weigh  out  5  grammes  of  the  butter  to  be  analysed,  and  care- 

fully transfer  it  to  a  clean  filter  funnel,  washing  the  remnants 
off  with  hot  water. 

2.  Pour  about  200  c.c.  of  hot  distilled  water  on  to  the  butter  and 

shake  up  well. 

3.  Pour  off  the  water  into  a  measuring  glass,  pipette  off  20  c.c. 

into  a  porcelain  evaporating  basin,  and  estimate  the  chlorine 
with  standard  silver  nitrate  as  in  the  case  of  water. 

EXAMPLE 

Butter  taken  .  .  .  5*2  grammes 

Measure  of  water  after  shaking  with  butter        220  c.c. 
Standard  AgNOg  required  for  20  c.c.  =  4"4  c.c. 

.*.  o'oo4  gramme  CI  are  present  in  20  c.c.  of  the  water 
.*.  butter  contains 

0-004       58*5       220       lOOo.      _  _^    _, 

3  X  ^— ^  X  —  X y  of  NaCl 

I         35'4      20      5.2/° 

=  I-427o 

Detection  of  Adulteration  with  Foreign  Fats 

The  most  important  chemical  examination  of  butter  is  the 
determination  of  the  presence  of  fats  which  are  not  those  of 
milk. 

Margarine,  which  now  is  a  good  and  cheap  substitute  for 
butter,  is  made  chiefly  of  beef  fat.  According  to  the  definition 
of  butter  given  above,  the  addition  of  beef  or  other  fat  to  butter 
is  a  legal  offence,  unless  the  mixture  is  sold  as  margarine,  and  it 
is  illegal  to  mix  more  than  10%  of  butter  fat  with  margarine. 

In  order  to  test  the  properties  of  butter  fat  and  margarine  fat 
it  is  necessary  to  obtain  these  free  from  water,  curd,  salt,  etc. 

Perhaps  the  simplest  method  of  doing  this  is  to  fill  a  beaker  of 
about  50  c.c.  capacity  with  the  butter  and  place  it  in  the  water 
oven  at  100°  C.  until  the  butter  has  melted,  and  the  water,  curd, 
etc.,  have  sunk  to  the  bottom. 


78  ANALYSIS   OF   BUTTER 

The  supernatant  fat  is  then  carefully  poured  on  to  a  dry  filter- 
paper — care  being  taken  that  no  water  gets  on  to  the  paper — and 
allowed  to  filter  into  a  clean  dry  beaker  in  the  oven. 

The  same  method  is  adopted  for  margarine.  In  the  process 
to  be  described,  although  butter  only  is  used,  it  will  be  under- 
stood that  exactly  the  same  procedure  is  to  be  adopted  for 
margarine. 

The  general  compositions  of  butter  and  margarine  fats  are — 


BUTTER 

MARGARINE 

Olein 

.       42'2I 

30-4 

Palmitin  and  stearin 

50-00 

69*2 

Butyrin 

4-67^ 

Caproin    . 

3-02   ■ 

0-4 

Caprylin    . 

O'lO 

lOO'OO 

,  lOO'O 

These  fats  are  the  salts  of  the  respective  fatty  acids  with 
glycerol.  Oleic,  palmitic  and  stearic  acids  are  termed  non- 
volatile or  insoluble  fatty  acids,  and  butyric,  etc.,  the  volatile  or 
soluble  acids. 

The  differences  in  the  composition  of  the  fats  are  responsible 
for  the  chemical  and  physical  properties  which  are  next  to  be 
determined. 

Estimation  of  the  Specific  Gravity 

The  procedure  is  similar  to  that  adopted  for  determining  the 
sp.  gr.  of  milk. 

Instead  of  weighing  at  the  room  temperature,  however,  the 
melted  butter  fat  and  the  clean  sp.  gr.  bottle  are  placed  in  an 
incubator  whose  temperature  is  37°  C,  for  an  hour.  The  bottle 
is  quickly  filled,  restoppered,  wiped,  and  replaced  in  the  incu- 
bator for  a  few  minutes.  It  is  then  weighed  as  quickly  as 
possible.  The  sp.  gr.  is  then  calculated  from  the  figure  thus 
obtained  and  that  obtained  on  weighing  the  same  bottle  full  of 
water  at  37""  C. 

EXAMPLE 

Weight  of  bottle  +  water  .         .         .      =  18-143  grammes 
„  „  .         .         .      =    8-401         „ 


Weight  of  water         .         .         .      =    9742 


DETECTION   OF   FOREIGN    FATS  79 

Weight  of  bottle  +  butter  .         .         .      =  17*279  grammes 
„  „  .         .         .      =   8-401         „ 


Weight  of  butter        .         .         .      =    8-878         „ 

8-878    , 

.-.  sp.  gr.  of  butter  = of  i 

^    ^  9*742 

=  0-9113 

The  sp.  gr.  of  true  butter  fat  is  never  below  0-91 1,  whereas 
that  of  margarine  never  rises  above  0-906. 

If  we  are  dealing  with  an  adulterated  butter,  the  estimation  of 
the  percentage  of  butter  present  is  merely  a  proportion  sum. 

EXAMPLE 

The  sample  had  a  sp.  gr.  of  908-5.  P'ind  the  percentage  of 
adulteration. 

We  must  accept  the  lowest  sp.  gr.  of  butter,  i.e.  911,  and  the 
highest  of  margarine,  906. 

X  X  906 +  (100  -  X)  911  =  100  X  908-5  'liH  ,J 

5.T=250 

^  =  50% 

The  Valenta  ^  Test  Modified  by  Jean 

This  test  depends  upon  the  different  amounts  of  glacial  acetic 
acid  taken  up  by  butter  and  margarine  respectively. 

Apparatus  required 

1.  A  graduated  test-tube  i  cm.  in  diameter. 

2.  A  graduated  pipette. 

3.  Water  bath. 

The  Process 

1.  Pour  3  c.c.  of  the  melted  fat  heated  to  50°  C.  into  the  test- 

tube  and  place  in  the  water  bath  at  50°  C. 

2.  By  means  of  the  pipette  add  3  c.c.  of  glacial  acetic  acid  to 

the  fat.     Leave  the  tube  in  the  water  bath  until  the  tempera- 
ture of  the  whole  of  the  contents  is  50°  G. 

^  The  original  Valenta  test  was  as  follows  :  Equal  parts  of  the  fat  and 
acetic  acid  were  mixed  together  and  heated  to  ioo°  C.  They  were  sub- 
sequently cooled  and  the  temperature  observed  at  which  a  cloudiness  appeared. 
This  was  found  to  occur  with  margarine  at  96-5°  C.  and  with  butter  at  61  "5°  C. 


8o  ANALYSIS   OF   BUTTER 

3.  Shake  well  two  or  three  times  and  return  to  the  bath.     Allow 

the  acetic  acid  to  settle  to  the  bottom   and  read  off  the 

height  of  the  acid,  i.e.  the  junction  between  the  acid  and  the 

oil. 

The  loss  in  volume  of  the  acetic  acid  represents  the  amount 

dissolved  by  the  fat. 

EXAMPLES 

Samples  of  butter  and  margarine  were  tested.  The  level  of 
the  acetic  acid  after  the  experiment  was  1*2  c.c.  in  the  butter  tube, 
and  2 "2  in  the  margarine  tube. 

I  '8 

.'.  acetic  acid  absorbed  by  butter  = — x  100  =  60% 

0-8 
„  „  „  margarine  =  — xioo=:26'6/^ 

o 
The  average  figures  are 

Butter      .....         63*3 

Margarine  .  .  .  .         266 

If  the  sample  submitted  to  analysis  comes  up  to  the  standard 
of  the  above  tests  it  can  be  certified  as  free  from  admixture  with 
foreign  fats.  If,  on  the  other  hand,  the  sample  is  below  the 
standards,  it  is  well  to  apply  a  further  test.  This  test  consists  in 
estimating  either  the  volatile  or  the  non-volatile  fatty  acids,  or 
both. 

ESTIMATION   OF   THE  VOLATILE   FATTY  ACIDS 

REICHERT-WOLLNY  PROCESS 

Apparatus,  etc.,  required 

1.  Globular  fiask  about  300  c.c.  capacity. 

2.  Small  Thorpe's  condenser. 

3.  Graduated  measures. 

4.  Graduated  burette. 

5.  Two  small  pieces  of  freshly  burnt  pumice. 

6.  Filter  funnel  and  paper. 

7.  Beakers  or  small  flasks. 

8.  — NaOH. 
10 

9.  Phenolphthalein. 

10.  50%  NaOH. 

11.  25%  sulphuric  acid. 


VOLATILE    FATTY   ACIDS  8i 

The  Process 

1.  5  grammes  of  the  filtered  butter  fat  are  poured  into  the  flask 

and  2  c.c.  of  the  50%  NaOHand  10  c.c.  of  absolute  alcohol 
are  added  to  the  butter. 

2.  A  reflux  condenser  is  fitted  to  the  flask,  and  the  latter  is 

placed  over  a  water  bath  at  100°  C.  The  flask  is  shaken 
from  time  to  time  and  the  boiling  continued  for  about  half 
an  hour. 

3.  The  condenser  is  disconnected  from  the  flask  and  the  alcohol 

is  allowed  to  evaporate. 

4.  100  c.c.  of  distilled  water  are  poured  in  the  flask,  the  whole 

shaken  up  well,  and  placed  on  the  water  bath  for  a  quarter 
of  an  hour. 

5.  4  c.c.  of  25%  H0SO4  are  mixed  with  36  c.c.  of  distilled  water 

and  poured  into  the  flask.  At  the  same  time  the  two  small 
pieces  of  pumice  are  dropped  in  the  flask. 

6.  A  cork  is  inserted  into  the  neck  of  the  flask,  carrying  a  tube 

bent  at  an  obtuse  angle  and  having  a  bulb  blown  on  it 
close  to  the  cork.  The  whole  is  then  connected  to  a  con- 
denser and  within  28-32  minutes  exactly  no  c.c.  are 
distilled  into  a  measure  through  a  funnel  carrying  a  filter- 
paper. 

7.  100  c.c.  of  the  distillate  are  taken,  and  to  this  i  c.c.  of  phenol- 

phthalein  is  added. 

8.  The  decinormal  caustic  soda  is  then  run  into  the  distillate 

until  a  permanent  rose-pink  is  obtained.  The  number  of 
c.c.  of  soda  is  noted.  To  the  number  used  one-tenth  is 
added. 

9.  This  number   of  c.c.   of  decinormal   soda   is    known   as    the 

"  Reichert-Wollny  Number  "  of  the  butter  or  fat.  Butter 
gives  a  Reichert-Wollny  number  of  not  less  than  24. 
Margarine  gives  a  Reichert-Wollny  number  of  not  less  than 
3.  Mixtures  of  margarine  and  butter  give  Reichert-Wollny 
numbers  between  3  and  24. 

Explanation 

Boiling  the  fat  with  alcoholic  soda  converts  the  glycerol  salts 
into  soda  salts  and  glycerin. 

C^^,{C,U.O.).  +  3NaOH  =  C3H,(HO)3  +  3NaC,H^02 

(glycerin)  (sod.  butyrate) 

6 


82  ANALYSIS    OF   BUTTER 

The  reaction  for  the  butyrate  is  similar  to  that  for  all  the  others, 
oleate,  stearate,  etc. 

The  addition  of  the  sulphuric  acid  decomposes  the  sodium 
butyrate,  etc.  ;  butyric  acid,  etc.,  are  set  free  and  are  distilled 
over  by  heat 

2NaC4H^Oo  +  H2SO4  =  Na2S04  +  2C4H8O2 

The  object  of  filtering  the  distillate  is  to  free  it  from  traces  of 
the  non-volatile  acids  which  almost  invariably  distil  over. 

Pumice  is  added  to  prevent  the  "  bumping  "  which  so  often 
accompanies  the  distillation  of  any  liquid  containing  sulphuric 
acid. 

EXAMPLE 

Five  grammes  of  butter  fat  gave  a  distillate,  100  c.c.  of  which 

N  .      . 

required  26-8  c.c.  of — NaOH  to  neutralize  it. 

Observe  that  no  c.c.  were  distilled  and  only  100  c.c.  neutral- 
ized.    The  acidity  of  the  whole  distillate  will  therefore  obviously 

be  —  X  26*8,  or  one-tenth  more   than    the   observed   quantity, 

namely,  29*48.     This  is  the    Reichert-WoUny    number   of  this 
butter  fat,  and  shows  genuine  butter. 

Suppose  the  figure  obtained  had  been  18.  What  percentage 
of  adulteration  with  margarine  would  this  show  ? 

Let  A:  =  the  percentage  of  adulteration  (i.e.  of  margarine). 
Then  A^-f  3  +  (100  -  .t)24  =100x18 

2ia:  =  6oo 

^^^  =  28-5% 

Notes 

The  Reichert-Wollny  number  does  not  give  an  exact  estima- 
tion of  the  volatile  fatty  acids  present  in  the  butter  fat.  It  is 
an  empirical  figure  only,  and  in  order  that  it  may  be  obtained 
accurately,  strict  care  must  be  taken  in  performing  the  various 
operations ;  the  apparatus  must  be  of  standard  Reichert-Wollny 
size ;  and  the  distillation  must  be  completed  within  the  specified 
time.  Under  such  standard  conditions  butter  fats  invariably  yield 
figures  over  24;  other  fats  (with  the  exception  of  cocoanut  oil) 
give  numbers  of  less  than  3.  Cocoanut  oil  may  give  a  Reichert- 
Wollny  number  at  7-8. 


INSOLUBLE  FATTY  ACIDS       83 

ESTIMATION  OF  THE  INSOLUBLE  FATTY  ACIDS 

Instead  of  estimating  the  volatile,  the  insoluble  fatty  acids  may 
be  estimated.  In  order  to  do  this,  the  fat  is  saponified  as  before. 
After  saponification  it  is  transferred  to  a  litre  flask,  and  the  small 
flask  is  washed  two  or  three  times  with  hot  water,  the  washings 
being  added  to  the  contents  of  the  large  flask.  4  c.c.  of  25% 
H2SO4  are  mixed  with  30  or  40  c.c.  of  hot  water  and  poured 
into  the  flask,  which  is  then  carefully  filled  to  within  an  inch  of 
the  top  of  the  neck  with  hot  water.  The  fatty  acids  will  now 
collect  on  the  top  of  the  water. 

The  mouth  of  the  flask  is  covered  over,  and  the  contents  are 
allowed  to  cool.  When  the  flask  is  cold,  the  mass  of  fatty  acids 
can  with  a  little  care  be  loosened  by  means  of  a  glass  rod  from 
the  sides  of  the  neck,  and  transferred  en  masse  to  a  clean  porce- 
lain evaporating  basin.  The  water  remaining  in  the  flask  is  now 
filtered  through  a  filter-paper,  and  when  the  filtration  is  complete 
both  paper  and  flask  are  allowed  to  dry. 

The  mass  of  fatty  acids  is  dissolved  in  ether  and  filtered 
through  the  dried  filter-paper  in  a  tared  platinum  dish,  and  the 
basin  is  washed  free  of  fatty  acids  with  a  little  ether.  The  large 
flask  is  now  washed  out  with  ether,  and  the  ether  filtered. 
Finally  the  filter-paper  is  washed  with  ether,  so  that  all  the  fatty 
acids  are  in  the  platinum  dish.  The  ether  is  next  evaporated  in 
the  water  oven,  and  the  dish  is  weighed.  The  gain  in  weight 
represents  the  amount  of  the  insoluble  fatty  acids. 

Note 

In  butter  fat  the  insoluble  fatty  acids  form  about  88%.  In 
margarine  and  other  fats  they  are  about  96%- 

Preservatives 

The  common  preservative  added  to  butter  is  boric  acid  or 
borax.  The  detection  of  this  is  performed  in  exactly  the  same 
manner  as  in  the  case  of  milk. 


84  ANALYSIS    OF   FLOUR 

ANALYSIS   OF   FLOUR 

A  GOOD   wheaten   flour   has    the    following  average   percentage 


composition  : — 

Starch 

•       597 

Soluble  nitrogen  . 

1-8 

Dextrin 

7'2 

Fat     . 

I'2 

Cellulose    . 

17 

Mineral  matter    . 

1-6 

Gluten 

12-8 

Water 

T4'0 

Total    . 

lOO'O 

The  chemical  analysis  of  a  sample  of  flour  for  adulteration  is 
usually  confined  to  the  determination  of  the  percentage  of  water, 
gluten,  ash,  and  mineral  matter. 

The  best  practical  and  domestic  test  to  apply  to  flour  is  to  use 
it  for  making  bread.     A  good  flour  makes  good  bread. 

ESTIMATION  OF  THE  PERCENTAGE  OF  WATER 

5  grammes  of  flour  are  weighed  in  a  platinum  dish,  and  dried  in 
the  water  oven  until  a  constant  weighing  is  obtained.  The  loss 
in  weight  represents  the  water  present,  and  the  percentage  is 
calculated  therefrom.  In  a  good  sample  of  flour  the  percentage 
of  water  should  not  exceed  18. 

ESTIMATION  OF  THE  ASH 

After  the  dried  flour  has  been  weighed  it  is  incinerated  in  the 
platinum  dish,  and  the  residue  weighed. 

The  percentage  of  ash  varies  from  o'5%  to  1%,  but  should  not 
exceed  this  latter  figure  unless  mineral  matter  has  been  added. 

ESTIMATION  OF  THE  GLUTEN 

1.  Weigh  50  grammes  of  flour,  mix  it  carefully  and  thoroughly  with 

50  c.c.  of  distilled  water,  and  allow  it  to  stand  for  an  hour. 

2.  Collect  the  paste  thus  made  in  a  linen  handkerchief,  and  make 

the  latter  into  a  bag. 

3.  Allow  water  from  a  tap  to  run  on  the  outside  of  the  bag  and 

knead  the  paste  well  until  the  water  running  away  is  clear. 

4.  Remove  the  paste  from  the  bag  and  complete  the  kneading  in 

the  hand  until  the  water  which  runs  away  is  quite  clear. 

5 .  Squeeze  the  mass  and  remove  all  the  extraneous  water  and  weigh. 
The    moist  gluten    should    form    from   25%    to    30%    of  the 

weight  of  the  flour. 

6.  Dry  the  gluten  in  a  platinum  evaporating  basin  and  weigh  again. 
The  dry  gluten  should  be  12%  to  15%  of  the  flour. 


BREAD  85 

Note 

Old  or  musty  flour  will  not  produce  an  adhesive  mass  which 
can  be  kneaded,  but  a  semi-liquid  mass  which  easily  washes 
away.  No  such  mass  of  gluten  can  be  obtained  with  rye  flour, 
however  good  and  new  it  may  be. 

ESTIMATION  OF  MINERAL  MATTER 

The  Chloroform  Test 

If  flour  which  contains  added  mineral  matter  be  shaken  up 
with  chloroform  the  flour  will  float  in  the  chloroform,  whilst  the 
mineral  matter  very  quickly  sinks  to  the  bottom. 

If  the  majority  of  the  chloroform  be  poured  off,  and  the 
sediment  shaken  up  with  fresh  chloroform  two  or  three  times, 
the  mineral  matter  can  be  obtained  free  from  flour. 

The  sediment  being  washed  out  of  the  test-tube  and  the  chloro- 
form evaporated,  is  now  ready  for  qualitative  examination. 

If  alum  has  been  added  to  the  flour  (a  rare  proceeding,  since 
it  is  not  usual  to  add  it  until  the  flour  is  in  the  process  of  bread- 
making)  it  will  be  detected  in  the  sediment,  as  it  is  only  very 
sparingly  soluble  in  chloroform. 

ERGOT 

Flour,  and  particularly  rye  flour,  is  liable  to  be  ergotized,  and  it 
is  necessary  for  the  student  to  know  how  to  detect  the  presence 
of  this  drug.  This  may  be  done  by  warming  some  of  the 
suspected  flour  with  a  solution  of  KOH.  If  ergot  is  present 
the  characteristic  odour  of  propylamine  will  be  detected. 

Ergot  may  also  be  detected  by  shaking  up  2  grammes  of  the 
suspected  flour  in  10  c.c.  of  70%  alcohol  containing  -h  HCl. 
If  ergot  is  present,  after  a  short  time  a  blood-red  colour  will 
develop. 


ANALYSIS  OF   BREAD 

An    average    sample 

of   bread    has    the 

following    percentage 

composition  : — 

Starch,  dextrin,  maltose    . 

51*3 

Proteins  . 

.... 

6-5 

Fat 

.         • 

i"o 

Ash 

.... 

I  'o 

Water      . 

• 

40*0 

lOO'O 

86  ANALYSIS   OF   BREAD 

The  chemical  analysis  of  a  sample  of  bread  is  usually  confined 
to  the  determination  of  the  acidity,  the  ash,  and  the  presence  of 
alum. 

THE  ESTIMATION  OF  THE  ACIDITY 

Acetic  and  lactic  acids  are  both  present  in  bread,  but  the 
acidity  is  usually  calculated  in  terms  of  acetic  acid. 

In  order  to  ascertain  the  acidity,  grate  a  certain  quantity  of  the 

bread  crumb  and  weigh  20  grammes  of  the  crumbs.     Transfer  these 

into  a  beaker  and  add  100  c.c.  of  hot  distilled  water.     Stir  well 

and  allow  it  to  stand  for  two  or  three  hours.     Filter  25  c.c.  into 

a  flask  or  evaporating  basin  and  add  a  drop  of  phenolphthalein. 

N  ... 

Add— NaOH  from  a  burette  until  the  fluid  is  neutral.     From 
10 

the  amount  of  alkali  used  calculate  the  amount  of  acid. 

EXAMPLE 

20  grammes  of  bread-crumb  were  taken. 

N 
2  K  C.C.  of  the  extract  took  0*6  c.c.  of  —  NaOH. 

The  20  grammes  of  bread  yielded  therefore  an  acidity  equal  to 

N 
^8"4  c.c.  of  — NaOH.     There  was  therefore  as  much  acid  as  in 
^    ^  10 

N  ... 

38*4  c.c.  of  —  acetic  acid.     The  molecular  weight  of  acetic  acid 

N         .         . 
is  60.    Therefore  100  c.c.  of — acetic   acid  contain  o*6  gramme 

of  acetic  acid. 

.    38-4 
.'.  38*4  c.c.  contain  ^^ —   x  o'6  gramme 

=  0*2304  gramme 

100  grammes  of  the  crumb  would  contain  5  x  0*2304,  i.e.  1*15 
grammes  of  acetic  acid. 

ESTIMATION  OF  THE  ASH 

The  estimation  of  the  ash  is  performed  in  a  manner  similar  to 
that  which  has  been  previously  described. 

If  the  ash  exceeds  2%  there  will  be  a  suspicion  of  added 
mineral  matter. 


ESTIMATION    OF   ALUM  87 

DETECTION  OF  ALUM 
In  order  to  detect  the  presence  of  alum  in  bread,  a  slice  should 
be  cut  from  the  middle  of  the  loaf  and  a  few  drops  of  a  mixture 
of  a  fresh  solution  of  logwood  in  alcohol  and  a  saturated  solution 
of  ammonium  carbonate  should  be  poured  on  to  the  centre  of  the 
slice.  When  the  fluid  dries  up  a  distinctly  blue  colour  will  develop 
if  alum  is  present.    If  no  alum  is  present  the  colour  will  be  brown. 

ESTIMATION  OF  ALUM 

The  estimation  of  alum  is  a  somewhat  lengthy  process,  but 
may  be  performed  in  the  following  manner  : — 

100  grammes  of  bread  are  carefully  incinerated  in  a  platinum 
dish  until  the  ash  does  not  decrease  in  weight.  After  cooling, 
3  c.c.  of  pure  strong  HCl  are  added,  and  the  whole  diluted  with 
20  or  30  c.c.  of  water.     The  fluid  is  then  boiled  and  filtered. 

The  residue  should  be  dried,  incinerated,  weighed  and  returned 
as  silica. 

The  filtrate  is  now  alkalized  with  ammonia,  when  the  phos- 
phates of  calcium,  magnesium,  iron,  and  aluminium  will  be 
thrown  down.  The  fluid  is  now  made  strongly  acid  with  acetic 
acid,  boiled,  and  filtered.  The  residue  consisting  of  the  phos- 
phates of  iron  and  aluminium  is  now  dried  and  weighed.  After 
the  weight  has  been  ascertained,  the  residue  is  dissolved,  the  iron 
estimated  colorimetrically  and  deducted  from  the  total  residue. 
The  remainder  will  represent  the  phosphate  of  aluminium,  and 
from  this  the  amount  of  alum  can  be  calculated. 

In  order  to  be  able  to  say  whether  alum  has  been  added  to 
bread  it  is  first  necessary  to  deduct  the  alumina  which  is  present 
normally  in  bread.  It  has  been  found  that  in  a  normal  sample 
of  bread  there  is  as  much  alum  as  silica.  The  weight  of  silica 
found  must  therefore  be  deducted  from  the  amount  of  alum 
found,  and  any  excess  will  represent  added  alum. 

ANALYSIS   OF   COFFEE 

Coffee  is  frequently  sold  mixed  with  chicory,  a  preparation  from 
the  root  of  the  wild  endive.  When  it  is  sold  as  a  mixture  no  legal 
objection  can  be  taken  to  it.  Sometimes  it  happens,  however, 
that  such  a  mixture  is  sold  as  pure  coffee  :  this  constitutes  a 
fraud,  and  it  becomes  necessary  to  know  whether  any  sample  of 
coffee  has  been  adulterated.  The  usual  adulterant  is  chicory, 
and  the  detection  of  this  substance  only  will  be  treated  here. 


88  ANALYSIS   OF   COFFEE 

Qualitative  Tests  for  Chicory 

A.  Put  some  of  the  suspected  coffee  upon  the  surface  of  some 

water  in  a  tall  beaker  or  cylinder.  Roasted  chicory  sinks 
at  once,  making  a  brown  trail  in  the  water  through  which  it 
passes ;  coffee  will  float  for  several  minutes,  and  takes 
longer  than  chicory  to  colour  the  water. 

B.  The  smell  of  chicory  is  different  from  that  of  coffee. 

C.  Examine  with  the  microscope.    Chicory  shows  typical  "  dotted 

ducts." 

D.  Heat  some  of  the  sample  in  a  platinum  dish  until  it  is  reduced 

to  ash.  The  ash  of  coffee  is  almost  white  ;  chicory  contains 
more  iron,  and  the  ash  has  a  reddish  colour. 

E.  Take  5  grammes  of  the  suspected  coffee,  and  pour  into  it  30  c.c. 

of  boiling  water.  Filter  into  a  Nessler  glass  and  add  5  c.c. 
of  lead  acetate  solution.  This  will  precipitate  the  colouring 
matter  of  coffee,  leaving  the  supernatant  fluid  colourless  ;  if 
chicory  is  present  the  column  of  fluid  will  retain  its  brown 
colour. 

ESTIMATION   OF  AMOUNT   OF   CHICORY 

FIRST  METHOD 

Specific  Gravity  of  a  10%  Extract 

1.  Weigh  exactly  10  grammes  of  the  sample  of  coffee,  and  place 

the  coffee  in  a  beaker. 

2.  Make  a  paste  of  the  coffee  with  a  little  distilled  water,  and 

then  dilute  so  that  exactly  100  c.c.  of  water  are  present. 

3.  Cover  the  beaker  and  leave  it  for  10  or  12  hours. 

4.  Filter  50  c.c,  fill  into  a  specific  gravity  bottle  and  weigh. 

5.  Calculate  the  specific  gravity,  and  from  this  the  percentage  of 

adulteration. 

EXAMPLE 

The  average  specific  gravities  of  10%  extracts  of  coffee  and 
chicory  are  respectively  I'oog  and  i'o24.  The  specific  gravity  of 
the  10%  extract  of  a  sample  of  mixed  coffee  and  chicory  was 
found  to  be  1*0139. 

If  X  is  the  percentage  of  coffee  in  the  mixture  it  is  obvious  that 
X  X  1009  +  (100  -  a:)io24  =  100  X  ioi3'9 

15^:=  1 010 

x=6rs 

That  is,  there  is  327%  of  chicory. 


ESTIMATION    OF   CHICORY 


89 


Table  giving  the  Approximate  Percentages  of  Coffee  in 
A  Mixture  of  Coffee  and  Chicory  from  the  Specific 
Gravity  of  a  10^  Extract. 


Percentage  of 

Sp.  gr.  of  10% 

Percentage  of 

Sp.  gr.  of  10% 

CofTee 

Extract 

Coffee 

Extract 

100 

1009  00 

45 

I0I7"25 

95 

100975 

40 

IOI80O 

90 

1010*50 

35 

101875 

85 

ion  '25 

30 

I0I9"50 

80 

1012  00 

25 

1 020 '25 

75 

101275 

20 

I02I*00 

70 

1013-50 

15 

IO2175 

65 

ioi4'25 

10 

1022  50 

60 

ioi5'oo 

5 

1023-25 

55 

101575 

0 

1024-00 

50 

ioi6*50 

~ 

SECOND  METHOD 
The  Determination  of  the  Soluble  Ash 

A  weighed  quantity  of  coffee  is  placed  in  a  platinum  dish  and 
incinerated.  After  cooling,  the  ash  is  treated  with  distilled  water 
until  all  the  soluble  matter  has  been  dissolved.  The  solution  is 
then  filtered,  the  dish  and  paper  washed  with  distilled  water,  the 
filtrate  transferred  to  a  tared  platinum  dish  and  evaporated  to 
dryness.  The  dish  is  then  weighed — the  increase  in  weight 
representing  the  amount  of  soluble  ash.  From  the  weight  the 
percentage  is  calculated.  In  order  to  determine  the  adulteration, 
it  is  assumed  that  chicory  never  yields  a  soluble  ash  greater  in 
amount  than  17%,  and  that  coffee  yields  a  soluble  ash  never  less 
than  3%. 


ANALYSIS   OF  SPIRITS 

These,  with  the  various  liqueurs,  contain  a  large  proportion  of 
alcohol.  The  Sale  of  Food  and  Drugs  Amendment  Act,  1879, 
fixes  the  minimum  of  alcohol  for  spirits. 

Whisky,  brandy,  and  rum  must  not  be  more  than  25  under 
proof. 

The  term  "proof  spirit"  arose  when  the  test  applied  was  to 
moisten  gunpowder  with  the  spirit  in  question.     On  applying  a 


90  ANALYSIS   OF   SPIRITS 

light,  if  the  gunpowder  burnt,  the  spirit  was  said  to  be  proof  or 
over  proof;  if  it  did  not,  it  was  under  proof.  It  has  been  subse- 
quently defined  by  Act  of  Parliament  to  be  a  mixture  of  alcohol 
and  water  of  such  a  density  that  the  weight  of  13  volumes  at 
51°  F.  shall  be  equal  to  that  of  12  volumes  of  water.  According 
to  this  definition,  proof  spirit  contains  49*24%  by  weight  and 
5  7 '06%  by  volume  of  alcohol. 

25  under  proof  corresponds,  therefore,  to  about  43%  by  volume 
of  absolute  alcohol. 

Gin  may  be  as  much  as  35  under  proof,  i.e.  need  only  contain 
about  37%  by  volume  of  alcohol. 

Alcohol 

To  determine  the  amount  of  alcohol  present  in  a  sample  of 
spirit.  Apparatus  required 

1.  Small  distilling  apparatus  with  Argand  burner. 

2.  Specific  gravity  bottle. 

The  Process 

1.  100  c.c.  of  the  spirit  are  measured  into  the  distilling  flask. 

2.  The  spirit  is  distilled  over  the  Argand  burner  until  it  is  all  but 

dry. 

3.  The  distillate  is  made  up  to  100  c.c.  by  the  addition  of  dis- 

tilled water  and  well  mixed. 

4.  The  specific  gravity  of  a  portion  of  this  is  now  taken  by  the 

aid  of  the  specific  gravity  bottle. 

5.  From  the  tables ^  the  percentage  of  alcohol  is  read. 

Acidity 

Nearly  all  spirits  have  a  slight  acidity,  due  either  to  volatile 
acids  (which  are  returned  in  terms  of  acetic  acid)  or  to  fixed 
acids  (which  are  returned  as  tartaric  acid). 

The  following  are  approximate  figures  : — 

TOTAL   ACIDITY  % 

Brandy         .  ...     o'oi  to  0*05 

Rum  .  .  .         .     o'5 

Whisky         .  .  .  .     o"! 

To  determine  the  acidity. 
I.  50  c.c.  of  the  spirit  are  measured  into  a  flask,  and  a  few  drops 
of  phenolphthalein  are  added. 

'■  These  tables  are  of  such  a  length  that  they  have  been  relegated  to  the 
Appendix. 


ANALYSIS    OF   SPIRITS  91 

2.  Decinormal  soda  is  added  drop  by  drop   until  the  point  of 

neutrality  is  arrived  at. 

3.  The  percentage  acidity  is  then  calculated. 

Brandy  being  made  from  grapes,  the   acidity  is  returned  in 

N 
terms  of  tartaric  acid  (i   c.c.  —NaOH  =  0-0075  gramme  tartaric 

acid). 

For  other  spirits  the  acidity  is  in  terms  of  acetic  acid  (i  c.c. 

—  NaOH  =  o"oo6  gramme  acetic  acid). 
10 

Sulphuric  acid  is  sometimes  present,  but  the  estimation  of  the 
free  acid  is  beyond  the  scope  of  this  work. 

The  residue  of  the  various  spirits  and  the  ash  resulting  from 
them  vary.  residue  %  ash  % 

Brandy     .         .         .     i  to  i"5  0*04  to  0*2 

Whisky     .         .         •     07  mere  trace 

Rum         .  .         .     07  to  i'5  o'l 

Gin  (sweetened)        .     5  to  6 

The  residue  is  obtained  by  evaporating  a  measured  quantity 
in  a  tared  platinum  dish,  and  weighing.  The  difference  in  weights 
is  the  amount  of  residue.  This  is  then  burnt,  and  the  ash 
weighed.     The  percentages  are  then  calculated. 

Tannin 

Any  amount  of  tannin  more  than  mere  traces  may  be  detected 
by  adding  a  few  drops  of  perchloride  of  iron  solution  to  the 
spirit.     A  darkening  in  colour  is  indicative  of  this  substance. 


ANALYSIS   OF  WINES 

The  determination  of  the  alcohol  and  the  residue  is  made  as 
in  the  analysis  of  spirits.  There  is  an  additional  determination 
necessary,  namely,  the  estimation  of  the  volatile  acidity. 

a.  Total  acidity. 

25  c.c.  of  the  wine  are  measured  into  a  beaker  and  titrated 

vv.   N  .  ... 

witn — NaOH,  the  colouring  matter  in  most  wines  acting  as  an 
10  '  °  ° 

effective  indicator.   The  acidity  is  returned  in  terms  of  tartaric  acid. 


92 


ANALYSIS    OF   WINES 


b.  Volatile  acidity. 

This  may  be  determined  in  two  ways  : — 

(i)  25  CO.  of  the  wine  are  diluted  with  200  c.c.  of  distilled  water 

and  distilled  until  only  about  20  c.c.  are  left  in  the  retort. 

N 
The  distillate  is  then  titrated  with  —  NaOH  and  the  acidity 


10 


(2) 


returned  in  terms  of  acetic  acid. 
25  c.c.  of  the  wine  are  evaporated  over  a  water  bath  almost 
to  dryness,  the  residue  is  dissolved  in   distilled  water  and 
titrated  as  before.     The  difference  between  the  total  acidity 
and  that  now  found  will  represent  the  volatile  acidity. 


Table  (after  Dupre)  showing  the  Proportions  of  the 
ABOVE  Constituents  in  a  few  Wines  (grammes  per  cent). 


Alcohol 

Fixed 

Volatile 

.    Total 

Dry 

acidity 

acidiiy 

acidity 

residue 

Hock          .       . 

9-56 

•348 

•057 

•420 

1-86 

Claret 

8-53 

•424 

•147 

•608 

2-14 

Sherry 

17-20 

270 

•153 

•461 

4  "20 

Madeira 

1775 

•326 

•168 

•536 

4 '34 

Port  . 

i8-5t> 

•308 

•084 

•413 

7-55 

Champagne 

9'22 

— 

— 

•5S0 

II '20 

Some  wines  contain  free  sugar,  whilst  others,  such  as  some  of 
the  Spanish  wines,  are  "  fortified  "  by  the  addition  of  alcohol. 


ANALYSIS   OF   BEER 

The  determinations  required  in  the  case  of  beer  are  alcohol, 
fixed,  volatile  and  total  acidity,  and  solid  residue,  and  the  opera- 
tions are  performed  exactly  as  in  the  case  of  wine. 

The  fixed  acidity  is  returned  in  terms  of  lactic  acid,  so  that  i  c.c. 

N 

— NaOH  =  0  000  gramme  lactic  acid. 
10  ° 

The  best  test  for  the  bitter  used,  whether  hop  or  other,  is  by 
means  of  the  taste. 

It  is  well  known  that  in  England  the  beer  is  brewed  with  what 
is  termed  a  top  yeast,  whilst  the  well-known  Lager  beers  are 
brewed  with  a  bottom  yeast.  In  consequence,  there  is  a  distinct 
difference  in  the  amount  of  alcohol  formed.  In  English  beers 
the  alcohol  forms  4%  to  6%,  in  German  beers  from  2%  to  5%. 


ANALYSIS    OF   BEER  93 

The  acidity  is  fairly  constant,  about  0*16%,  and  the  residues  vary 
from  2-5  to  15%. 

Arsenic  in   Beer 

During  the  winter  of  1 900-1 901  there  was  a  large  outbreak  of 
arsenical  poisoning  among  beer-drinkers,  chiefly  in  the  northern 
parts  of  England.  The  beer  that  gave  rise  to  this  poisoning  had 
been  manufactured,  not  from  malt,  but  from  invert  sugar,  which 
was  prepared  by  the  action  of  dilute  sulphuric  acid  on  rice  and 
other  starches.  Dilute  commercial  sulphuric  acid  may  contain 
arsenic,  derived  from  the  iron  pyrites  used  in  its  manufacture, 
and  some  invert  sugars,  made  by  this  process,  yield  as  much  as 
two  grains  of  arsenious  acid  to  the  pound.  Some  of  the  beers 
analysed  during  the  outbreak  of  poisoning  showed  as  much  as 
a  grain  per  gallon  of  arsenious  acid,  which  is  one  hundred  times 
the  maximum  allowed  by  the  Royal  Commission  on  Arsenical 
Poisoning. 

Test  for  Arsenic 

The  most  convenient  test  for  this  metal  is  that  of  Reinsch. 
Some  of  the  beer  is  placed  in  a  beaker,  and  acidulated  by  dilute 
pure  hydrochloric  acid.  A  small  piece  of  bright  arsenic-free 
copper  foil  is  suspended  in  the  liquid,  and  the  whole  is  then 
boiled  for  half  an  hour  and  allowed  to  cool.  If  the  copper  foil 
is  unaffected,  no  arsenic  is  present :  if,  on  the  other  hand,  there 
is  a  grey  or  black  deposit,  then  arsenic  (or  antimony)  is  probably 
contained  in  the  beer.  The  copper  foil  is  then  washed  with 
water,  dried,  and  placed  in  a  test-tube  over  the  mouth  of  which  is 
a  cover-glass.  The  tube  is  heated  gently  over  a  Bunsen  burner, 
when  the  arsenic  is  oxidized  and  sublimes  and  condenses  on  the 
cool  part  of  the  tube  and  on  the  cover-glass.  Upon  examining 
the  deposit  under  the  microscope  the  tetrahedral  or  octahedral 
crystals  of  arsenious  oxide  are  seen.  If  the  deposit  on  the  copper 
is  antimony,  the  microscopic  examination  shows  only  an  amor- 
phous deposit. 

With  suitable  and  obvious  modifications  this  test  of  Reinsch  for 
arsenic  may  be  applied  to  the  detection  of  the  metal  in  food, 
artificial  flowers,  wall-papers  and  other  substances  in  \yhich  the 
presence  of  arsenic  is  suspected. 

VINEGAR 

Vinegar  is  the  well-known  condiment,  the  essential  ingredient 
of  which  is  acetic  acid. 


94  ANALYSIS    OF   VINEGAR 

Two  points  are  important  concerning  vinegar.  First,  that  it 
shall  contain  at  least  3%  of  acetic  acid,  and  secondly,  that  it  shall 
not  contain  more  than  the  merest  traces  of  free  mineral  acid. 

Estimation  of  the  Acetic  Acid 

N 
The  vinegar  may  be  titrated  directly  with  — NaOH,    usmg 

phenolphthalein  as  indicator.     10  c.c.  of  the  vinegar  are  diluted 

with  an  equal  quantity  of  distilled  water  before  titrating.     The 

...  N 

acetic  acid  is  calculated  directly  from  the  soda  :   i  c.c.  — NaOH 

10 

=  o"oo6  gramme  acetic  acid. 

Detection  of  Free  Mineral  Acid 

Sulphuric  acid  is  the  acid  most  commonly  found,  although 
hydrochloric  acid  has  been  found.  The  detection  of  free  acid 
is  easily  determined  by  placing  a  few  drops  of  vinegar  and  a  drop 
of  a  watery  solution  of  methyl  violet  upon  a  white  slab,  the  two 
fluids  being  separate.  With  a  glass  rod,  a  portion  of  the  methyl 
violet  is  brought  into  contact  with  the  vinegar.  If  no  free 
mineral  acid  is  present  the  colour  remains.  If  only  a  trace  of 
free  acid  is  present  the  violet  changes  to  blue,  and  if  more  than 
•1%  is  present  a  distinctly  green  colour  develops. 

A  further  test  consists  in  testing  the  reaction  of  the  ash.  If  a 
pure  sample  of  vinegar  be  incinerated  the  ash  will  be  alkaline, 
owing  to  the  fact  that  the  organic  salts  are  converted  into  car- 
bonates upon  heating.  If  free  mineral  acid  is  present  the  ash 
will  be  less  alkaline,  or  even  neutral  if  more  than  traces  are 
present. 

LEMON    JUICE    AND    LIME    JUICE 

These  juices  are  always  kept  on  board  ship,  and  the  Board  of 
Trade  standards  are  that  the  juice  shall  have  a  specific  gravity  of 
at  least  1*030,  and  shall  have  an  acidity  equal  to  30  grains  per 
ounce  of  citric  acid  (6'8%). 

The  specific  gravity  is  determined  in  the  manner  previously 
described. 

The  acidity,  which  is  due  to  the  presence  of  citric  and  malic 

N  N 

acids,  is  determined  by  titratinoj  with  — NaOH  (i  c.c.  — NaOH 

10  ^10 

=  0.006  gramme  citric  acid),  and  returned  in  terms  of  citric  acid. 

Free  mineral  acids  are  determined  as  in  the  case  of  vinegar. 


ANALYSIS   OF  AIR 

ESTIMATION  OF  OXYGEN   IN  AIR 

Apparatus,  etc. 

1.  Hempel's  gas-absorption  bulbs. 

2.  Two  graduated  cylinders,  one  furnished  with  a  fine  nozzle  and 

glass  tap,  and  bent  at  right  angles  at  the  other  end,  and  the 
second  one  bent  at  right  angles  at  one  end  and  funnel-shaped 
and  open  at  the  other,  the  two  bent  ends  fitting  in  wooden 
supports  and  connected  together  with  indiarubber  tubing, 
2  ft.  The  rubber  tubing  should  not  connect  the  two  tubes 
directly,  but  should  have  a  piece  of  glass  tubing  inserted 
about  the  centre. 

3.  An  alkaline  solution  of  pyrogallic  acid. 

The  Process 

1.  Fill  the  Hempel  bulbs  with  the  pyrogallic  acid  so  that  the 

lower  bulb  is  full  and  the  level  of  the  pyrogallic  acid  in  the 
U-shaped  capillary  tube  at  a  certain  point,  which  is  recorded 
by  making  a  pencil  mark  on  the  white  enamel  behind. 
Attach  short  lengths  of  rubber  tubing  to  the  open  ends,  and 
clamp. 

2.  Place  the  two  cylinders  A  (the  one  provided  with  a  stop-cock 

and  nozzle)  and  B  (the  levelling  tube)  on  the  table  and  pour 
water  into  B  until  each  tube  is  about  half  full.  Now  raise 
B.  The  air  in  A  will  be  expelled  as  the  level  of  the  water 
rises.     When  all  the  air  is  expelled  close  the  tap. 

3.  The  apparatus  being  in  the  place  whose  air  is  to  be  examined, 

the  tube  B  is  lowered  and  the  stop-cock  of  A  opened.  The 
air  will  enter  into  A.  When  about  50  c.c.  have  entered,  the 
stop-cock  is  closed,  ^is  now  raised  or  lowered  as  required 
to  bring  the  water  in  the  tubes  to  the  same  level,  and  the 
quantity  of  air  noted. 

4.  The  capillary  tube  of  the  absorption  bulb  is  connected  with 

the  nozzle  of  ^  by  the  short  indiarubber  tube  and  the  clamp 
undone. 

95 


96 


ANALYSIS   OF   AIR 


5.  The  stop-cock  of  ^  is  now  opened  and  the  tube  B  is  raised. 
The  air  is  by  this  means  driven  over  into  the  absorption 
bulb.  The  stop-cock  is  now  closed.  The  bulb  may  be 
carefully  disconnected  after  clamping  the  tube,  and  shaken 
gently. 


B 


FIG.    I.       HEMPEL's    liULB 


ESTIMATION   OF   CARBON    DIOXIDE       97 

6.  After  about  15   minutes  the  tube  ^  is  again  connected,  the 

stop-cock  opened,  and  the  tube  B  lowered  until  the  level  of 
the  pyrogallic  acid  in  the  capillary  tube  is  the  same  as 
before  the  operation. 

7.  The  tube  B  is  again  adjusted  so  that  the  level  of  the  water  in 

A  and  B  is  the  same,  and  the  quantity  of  air  in  A  is  noted. 

The  difference  between  the  first  and  second  readings  will  give 
the  amount  of  oxygen  absorbed,  and  this  difference  multiplied  by 
100  and  divided  by  the  original  bulk  will  give  the  percentage  of 
oxygen  in  the  air. 

Expired  air  may  be  examined  in  the  same  manner.  In  order 
to  collect  the  expired  air,  the  tube  A  should  be  filled  w4th  water 
by  raising  A  as  before,  and  the  air  may  be  simply  blown  dow^n 
the  nozzle  from  the  mouth. 

This  method  is  not  sufficiently  delicate  for  the  estimation  of 
COo  in  ordinary  air,  and  other  methods  have  to  be  adopted. 
These  are  described  below. 

ESTIMATION   OF  CARBON   DIOXIDE 

I.   PETTENKOFER'S   METHOD 
Apparatus,  etc. 

1.  A  large  bottle. 

2.  A  50  c.c.  and  a  25  c.c.  pipette. 

3.  A  50  c.c.  burette. 

4.  A  small  Erlenmeyer  flask. 

5.  Standard  oxalic  acid^,  i  c.c.  =0*5  c.c.  CO2. 

6.  Baryta  water. 

7.  Solution  of  methyl  orange  or  phenolphthalein. 

The  Process 

1.  The  large  jar  must  be  accurately  gauged  by  filling  with  water 

to  the  top  and  inserting  the  stopper,  and  then  measuring  the 
amount  of  water. 

2.  To  fill  the  jar  with  the  air,  first  fill  it  with  water  and  empty 

the  water  in  the  room,  the  air  of  which  is  to  be  sampled. 

3.  Add   50  c.c.   of  baryta  water  by  means  of  the  pipette  and 

replace  the  stopper.  Shake  up  well  and  allows  the  jar  to 
stand  for  about  an  hour,  shaking  from  time  to  time. 

4.  Meanwhile,  measure  25  c.c.  of  the  baryta  w^ater  into  an  Erlen- 

meyer flask,  add  a  drop  of  methyl  orange  and  titrate  with 
the  standard  oxalic  acid.     Note  the  number  of  c.c.  used. 


98  ANALYSIS   OF   AIR 

5.  When  the  baryta  water  has  been  in  contact  with  the  air  for  a 

sufficiently  long  time,  remove  25  c.c.  of  the  baryta  water 
with  the  pipette  and  allow  it  to  run  into  another  Erlenmeyer 
flask. 

6.  Add  a  drop  of  methyl  orange  and  titrate  with  the  oxalic  acid, 

noting  the  number  of  c.c.  used. 

Explanation 

The  baryta  water  when  in  contact  with  the  CO2  absorbs  it,  and 
barium  carbonate  is  formed,  which  is  insoluble. 

Ba(0H)2  +  CO2  =  BaCOg  +  Ufi 

As  BaC03  is  an  insoluble  neutral  salt,  the  alkalizing  power  of 
the  Ba(HO)o  is  diminished  in  proportion  to  the  amount  of  the 
salt  formed. 

In  titrating  with  the  oxalic  acid  the  BaCO.  is  unaffected  by  the 
weak  acid,  and  the  whole  of  the  acid  used  is  expended  in  con- 
verting the  Ba(0H)2  into  Ba(COO)o. 

Ba(OH)2  +  (COOH)2  =  Ba(COO)o+  2H2O 
Therefore  the  difference  between  the  quantity  of  oxalic  acid  used 
to  neutralize  the  25  c.c.  of  Ba(0H)2  which  has  not  been  in 
contact  with  the  air,  and  that  required  to  neutralize  the  Ba(0H)2 
which  has  been  in  contact  with  the  air,  will  represent  the  amount 
of  Ba(0H)2  converted  into  BaCOo. 

But  the  oxalic  acid  was  prepared  so  that  i  c.c.  should  be  the 
equivalent  of  0*5  c.c.  of  CO2 ;  therefore  each  c.c.  of  difference 
=  o*5  c.c.  of  COo  which  has  converted  the  Ba(0H)2  into  BaCOg. 

EXAMPLE 

The  jar  was  found  to  contain  3950  c.c. 

50  c.c.  of  baryta  water  were  run  into  the  jar,  therefore  the  air 
experimented  upon  was  3950  —  50  =  3900  c.c. 

On  titrating  the  Ba(0H)2  it  was  found  that  25  c.c.  of  the  fresh 
solution  required  22*50  c.c.  of  standard  acid  to  neutralize. 
The  Ba(0H)2  from  the  jar  took  i9"35  c.c. 

25  c.c.  of  original  Ba(0H)2      .         .      =22*50  c.c.  acid 
25  c.c.  of  used  Ba(0H)2.         .         .      =19*35    »       >> 

Difference  of  acid  used    .         .      =    3*15    ,,       ,, 

But  I  c.c.  acid  =  0*5  c.c.  COg  at  0°  C.  and  760  mm.  of  mercury, 
.'.  CO2  taken  up  by  25  c.c.  of  Ba(0H)2  =  3.15  c.c. 


ESTIMATION    OF    CARBON    DIOXIDE       99 

As  50  c.c.  were  used,  the  COg  absorbed  by  the  Ba(0H)2  = 
3.15  C.C. 

Now  this  3*15  c.c.  were  present  in  3900  c.c. 

.-.  there  were  3*15  x  logo  c.c.  of  C02%  -  0*80% 

Notes 

In  manipulating  the  jar  for  emptying,  filling,  etc.,  care  must  be 
taken  not  to  handle  it  with  the  naked  hands,  as  by  so  doing  the 
sides  of  the  jar  will  get  heated,  and  the  volume  will  not  be 
correctly  obtained,  since  the  air  will  expand. 

The  baryta  water  must  be  run  into  the  jar  and  removed  with 
all  expedition,  and  care  must  be  taken  not  to  breathe  into  the  jar 
during  any  of  the  manipulations.  The  same  care  must  be  taken 
with  the  flasks  during  titration,  etc. 

It  is  not  necessary  to  wait  for  the  baryta  water  to  clear  before 
pipetting  it  out  for  titration,  since,  as  has  been  said,  dilute  oxalic 
acid  does  not  decompose  the  barium  carbonate. 

In  calculating  the  COo  present  per  thousand  in  the  jar,  in  the 
above  example,  no  notice  has  been  taken  of  the  fact  that  i  c.c. 
of  the  acid  corresponds  to  i  c.c.  of  CO.,  at  0°  C.  and  760  mm.  of 
mercury,  and  not  to  i  c.c.  at  the  room  temperature  and  pressure. 

To  correct  for  this  it  is  only  necessary  to  multiply  the  3"  15  by 

760  T 

-TT)  and  this  by  ,  when  P  is  the  height  of  the  barometer,  and 

P  ^  273  °  ' 

Z'the  absolute  temperature  of  the  room. 

Standard  Oxalic  Acid 

(i  C.C.  =o-5  c.c.  CO2  at  N.T.P.) 

It  is  convenient  to  have  the  oxalic  acid  of  such  a  strength  that 
I  c.c.  of  it  neutrahzes  as  much  Ba(0H)2  or  Ca(0H)2  as  0*5  c.c. 
of  COo.  Now  I  c.c.  of  COq  weighs  22x0*0000895  grammes 
=  o'ooi969  gramme.  Oxalic  acid  crystallizes  with  2  molecules  of 
H2O,  its  molecular  weight  is  therefore  126,  for  the  formula  will 
be  (C00H)2  + 2H2O.  Therefore  in  i  c.c.  of  the  standard 
solution  there  must  be 

1  ^ 126    .  o°ooi96q  ^ 

-of of grammes  =  0*0028 iQ2t;   gramme. 

2  44  I  °  :7    J    o 

For  convenience  a  stronger  solution  than  this  is  made  by  dissolv- 
ing 28*19  grammes  of  crystallized  oxalic  acid  in  a  litre  of  freshly 
boiled  distilled  water.     Each  c.c    of  this  will  be  equivalent  to 


100  ANALYSIS   OF   AIR 

5  c.c.  of  CO2;  when  the  acid  is  required  for  use,  10  c.c.  of  the 
strong  acid  are  diluted  with  90  c.c.  of  distilled  water;  i  c.c.  of 
the  weak  acid  then  equals  0*5  c.c.  COg. 

2.   HALDANE'S    METHOD 

Haldane  has  devised  a  small  and  portable  gas  analysis 
apparatus  for  the  estimation  of  carbon  dioxide  in  air.  The 
advantages  claimed  by  it  are  that  the  estimation  can  be  completed 
in  a  few  minutes,  only  a  small  volume  of  air  is  required,  and  the 
apparatus  is  easily  portable :  the  disadvantages  are  the  relatively 
large  cost,  and  the  difficulty,  to  the  beginner,  of  manipulation. 
The  results  obtained  by  it  are  sufficiently  accurate  for  practical 
purposes ;  the  principle  on  which  the  analyses  are  made  being 
the  absorption  of  the  COo  by  means  of  potash.  Full  details  are 
given  in  text  books  larger  than  this,  and  are  supplied  also  with 
the  apparatus  itself. 

Detection  of  Carbon   Monoxide  in  Air 

If  CO  is  present  in  the  air  or  any  mixture  of  gases  in  any 
considerable  quantity  it  may  be  absorbed  by  a  solution  of  cuprous 
chloride ;  if  it  is  only  present  in  minute  percentage  this  method 
is  quite  useless. 

If  a  sample  of  the  suspected  air  be  shaken  up  with  a  few  c.c. 
of  a  I  %  solution  of  blood,  the  latter  acquires  a  pink  colour  which 
is  quite  different  from  the  colour  of  the  normal  blood. 

Blood  thus  treated  with  carbon  monoxide  gives,  in  weak 
solution,  a  characteristic  spectrum,  showing  two  well-marked 
bands  with  sharp  edges  in  the  yellow  and  green  parts  of  the 
spectrum  :  when  the  blood  is  treated  with  dilute  ammonium 
sulphide  these  bands  persist,  in  contradistinction  to  oxy- 
haemoglobin,  which  loses  the  bands  after  such  reduction.  The 
persistence  of  these  two  bands  after  reduction  with  (NH4)2S 
means  that  carbon-monoxide-haemoglobin  is  present,  and  that 
CO  was  present  in  the  air  that  was  tested. 

Estimation  of  Carbon  Monoxide  in  Air 

The  following  account  is  that  of  Haldane,  who  elaborated  the 
method : — 

Estimation  of  the  Degree  of  Saturation  of  Blood  with  CO 

"  When  only  a  rough  quantitative  estimate  of  the  percentage 


CARBON    MONOXIDE    IN    AIR  loi 

saturation  is  required,  as  in  ordinary  post-mortem  examinations 
or  in  examining  the  blood  of  a  patient  suffering  from  gas  poison- 
ing, all  that  is  necessary  is  to  prepare  in  three  test-tubes  of  even 
size  (i)  a  solution  of  normal  blood  well  diluted;  (2)  some  of 
the  same  solution  saturated  with  coal  gas ;  and  (3)  a  solution  of 
the  suspected  blood  diluted  to  the  same  depth  of  colour  as  the 
other  two  solutions.  One  can  then  tell  roughly  by  the  relative 
pinkness  of  the  suspected  blood  to  what  extent  it  is  saturated/' 

To  measure  accurately  the  extent  to  which  blood  is  saturated 
with  CO  he  devised  the  following  method : — 

"A  solution  of  about  i  of  normal  blood  to  100  of  water  is 
made ;  also  a  solution  of  carmine  dissolved  with  the  help  of  a 
little  ammonia,  and  diluted  till  its  depth  of  tint  is  about  the  same 
as  that  of  the  blood  solution.  Two  test-tubes  of  equal  diameter 
(about  half  an  inch)  are  then  selected.  Into  one  of  these  5  c.c. 
of  the  blood  solution  are  measured  with  a  pipette ;  into  the  other 
about  an  equal  quantity  is  poured.  Ordinary  lighting  gas  is  then 
allowed  to  blow  into  the  second  test-tube  through  a  piece  of 
rubber  tubing  for  a  few  seconds.  The  test-tube  is  then  quickly 
closed  with  the  thumb  before  the  gas  has  had  time  to  escape,  and 
the  blood  solution  thoroughly  shaken  up  with  the  gas  for  a  few 
seconds.  The  haemoglobin  is  thus  completely  saturated  with 
carbonic  oxide,  and  the  solution  has  now  the  characteristic  pink 
tint.  The  carmine  solution,  which  has  a  still  pinker  tint,  is  now 
added  from  a  burette  to  the  5  c.c.  of  normal  blood  solution  in 
the  other  test-tube  until  the  tints  are  the  same  in  the  two  test- 
tubes.  Not  only,  however,  must  the  tints  be  equal  in  quality^ 
but  they  must  also  be  sensibly  equal  in  depth.  If  the  carmine 
solution  is  too  strong  or  too  weak,  the  latter  will  not  be  the  case, 
and  the  solution  must  be  diluted  or  made  stronger  accordingly. 
It  is  usually  easiest  to  make  the  carmine  a  little  too  strong  at 
first,  so  that  on  adding  both  carmine  solution  and  water  equality 
can  be  established.  From  the  amount  of  water  which  required  to 
be  added  it  is  easy  to  calculate  the  extent  to  which  the  original 
carmine  solution  needs  to  be  diluted.  The  solutions  are  now 
ready  for  use,  and  the  actual  analysis  is  made  as  follows  :  5  c.c. 
of  the  solution  of  normal  blood  are  measured  into  one  of  the 
test-tubes,  and  a  drop  of  the  suspected  blood  placed  in  the  other 
test-tube  and  cautiously  diluted  with  water  till  its  depth  of  tint  is 
about  equal  to  that  of  the  normal  solution.  If  carbonic  oxide  be 
present  in  the  haemoglobin,  a  difference  of  quality  in  the  tints  of 
the    two    solutions    will    now  be    clearly  perceptible.     Carmine 


102  ANALYSIS   OF   AIR 

solution  is  then  added  from  the  burette  to  the  normal  blood,  and 
water,  if  necessary,  to  the  abnormal  blood,  till  the  tints  are  equal 
in  both  quality  and  depth.  The  carmine  is  added  by  about 
o"2  c.c.  at  a  time,  the  points  being  noted  at  which  there  is  just 
too  little  and  just  too  much  carmine,  and  the  mean  being  taken. 
The  solution  of  abnormal  blood  is  then  saturated  with  coal  gas, 
and  the  addition  of  carmine  to  the  other  test-tube  continued 
until  equality  is  again  established,  and  the  amount  of  carmine 
noted.  The  percentage  saturation  with  carbonic  oxide  of  the 
abnormal  blood  can  now  be  easily  calculated,  since  we  know  how 
much  carmine  solution  its  saturation  represented  as  compared 
with  what  complete  saturation  represented. 

"  The  method  of  calculation  is  illustrated  by  the  following 
example  :  To  5  c.c.  of  normal  blood  solution,  2*2  c.c.  of  carmine 
is  required  to  be  added  to  produce  the  tint  of  the  blood  under 
examination,  and  6"2  c.c.  to  produce  the  tint  of  the  same  blood 
fully  saturated.  In  the  former  case  the  carmine  was  in  the 
proportion  of  2*2  in  7*2  and  in  the  latter  of  6'2  in  11 '2.  The 
percentage  saturation  (v)  of  the  haemoglobin  with  carbonic  oxide 
is  thus  given  by  the  following  proportion  sum  : — 

6'2      .    2'2 

.  —  .  I  100  I  a: 

11*2        7*2 

X  is  therefore  =  55*2.  As  the  compound  of  carbonic  oxide  and 
haemoglobin  is  to  a  slight  extent  dissociated  when  the  blood  is 
diluted  with  water,  the  value  found  is  a  little  too  low.  The 
corrections  needed  are  as  follows  :  Add  0*5  if  30%  saturation  be 
found,  I'l  if  50%,  i"6  if  60%,  2-6  if  70%,  4*4  if  80%,  lo-o  if 
90%.  Thus,  in  the  above  example,  we  must  add  1*3,  so  that  the 
true  saturation  is  56*5%.  In  comparing  the  tints  the  test-tubes 
should  be  held  up  against  the  light  from  a  window,  but  bright 
light  should  be  avoided  as  much  as  possible,  as  it  increases  the 
dissociation.  Failing  daylight,  an  incandescent  burner  with  a 
chimney  of  blue  glass  and  an  opal  globe  may  be  used  as  the 
source  of  light. 

"  Haemoglobin  brought  into  intimate  contact  with  air  containing 
0*07%  of  CO  will  finally  reach  a  state  of  equilibrium  in  which  it 
is  saturated  to  an  equal  extent  with  CO  and  oxygen.  If  the 
percentage  of  CO  or  oxygen  in  the  air  be  increased  or  diminished, 
there  will  be  an  exactly  corresponding  increase  or  diminution  of 
the  relative  share  of  the  haemoglobin  which  either  gas  obtains. 
Air  containing  2  xo'o7  =  0-14%  of  CO  will,  for  instance,  produce 


CARBON    MONOXIDE    IN    AIR  103 

two-thirds  saturation  with  CO,  and  one-third  saturation  with 
oxygen,  and  so  on.  In  the  living  body  the  proportion  of  CO 
taken  by  the  hcemoglobin  from  respired  air  containing  a  given 
percentage  of  CO  is  not  so  large  as  outside  the  body,  about  o'i% 
of  CO  in  the  air  breathed  being  necessary  to  produce  half  satura- 
tion of  the  hsemoglobin.  The  general  law  of  absorption  is, 
however,  much  the  same,  and  it  follows  that  there  is  a  certain 
maximum  of  saturation  for  each  percentage.  With  less  than 
0*05%  of  CO  in  the  air  this  maximum  does  not  exceed  33% 
saturation,  and  the  corresponding  symptoms  are  scarcely  appreci- 
able, except  on  muscular  exertion.  With  more  than  about  0*2% 
the  maximum  exceeds  60%  saturation. 

"The  detection  and  determination  of  small  percentages  of  CO 
in  air  was  formerly  a  matter  of  great,  and  often  almost  insuper- 
able, difficulty.  I  have  recently,  however,  introduced  a  simple, 
and  I  think  very  satisfactory,  method,  depending  on  the  already 
described  action  of  CO  on  blood  solution  in  presence  of  air.  The 
sample  of  air  is  collected  in  a  clean  and  dry  bottle  of  about  4  oz. 
capacity.  The  cork  of  the  bottle  is  removed  in  the  laboratory 
under  a  0*5%  solution  of  blood,  and  about  5  c.c.  of  the 
air  allowed  to  bubble  out,  a  corresponding  volume  of  the  blood 
solution  entering.  The  cork  is  then  replaced,  covered  with  a 
cloth  to  keep  off  the  light,  and  shaken  continuously  for  about 
ten  minutes,  when  the  haemoglobin  will  have  reached  the  point  of 
saturation  corresponding  to  the  percentage  of  CO  present.  The 
solution  is  then  poured  out  into  a  test-tube,  and  the  saturation 
determined  with  carmine  solution  in  the  manner  described  above. 
It  is  evident  that  as  in  each  case  the  saturation  found  corresponds 
to  a  definite  percentage  of  CO  in  the  air,  it  is  easy  to  calculate 
this  percentage.  If  /  be  the  percentage  required,  and  s  the 
percentage  saturation  found,  p  is  calculated  from  the  following 

formula  :—  ^  ^  o-o^ 

p  = '- 

100  —  s 

Thus,  [{s  =  6o,  p  is  0*105.  This  method  may  also  be  used  for 
the  direct  determination  of  carbonic  oxide  in  lighting  gas.  The 
latter  must,  however,  be  first  diluted  to  yj^  (or  with  carburetted 
water-gas  to  ^^q)  with  air.  As  it  is  quite  easy  to  make  this 
dilution  with  perfect  accuracy,  the  method  is  an  exact  one,  and  is 
not  only  rapid,  but  avoids  the  difficulties  and  sources  of  error 
connected  with  the  ordinary  method  of  determination  by  cuprous 
chloride,  or  by  explosion." 


104  ANALYSIS   OF   AIR 

Ozone 

Ozone  (O3),  an  allotropic  modification  of  oxygen,  is  found  in 
the  air  in  the  neighbourhood  of  the  sea  and  after  electric 
discharges. 

In  order  to  detect  its  presence  in  the  atmosphere,  a  piece  of 
blotting-paper  is  saturated  with  a  solution  of  KI  and  starch,  and 
exposed  to  a  current  of  air  for  from  six  to  twenty-four  hours, 
shaded  meanwhile  from  the  sun.  If  ozone  is  present  the  paper 
will  have  acquired  a  blue  tinge  from  the  liberation  of  iodine 
from  the  potassium  iodide,  and  subsequent  combination  of  the 
iodine  with  the  starch. 

In  the  neighbourhood  of  chemical  works  the  above  test  is  not 
available,  since  other  gases,  such  as  chlorine,  will  cause  the 
appearance  of  the  blue  colour.  Instead,  two  strips  of  neutral 
litmus  paper  are  taken,  one  of  which  has  been  steeped  in  KI 
solution,  and  exposed  to  the  air.  If  ozone  is  present  the  litmus 
paper  soaked  in  KI  will  be  turned  blue  from  the  conversion  of 
the  KI  into  KoO  by  the  ozone.  The  control  litmus  paper  is  in 
order  to  ensure  the  absence  of  ammonia. 


Noxious  Gases  in  Air 

The  air  in  the  neighbourhood  of  chemical  and  other  works 
frequently  contains  traces  of  chlorine,  hydrochloric  acid,  sulphur 
dioxide,  and  various  other  gases.  These  gases  when  concen- 
trated are  certainly  harmful ;  but  when  diluted  with  air,  as  they 
are  usually  found,  their  danger  to  life  is  doubtful.  The  student 
for  D.P.H.  examinations,  however,  is  expected  to  be  able  to 
identify  various  gases,  which  are  generally  supplied  to  him  in 
the  undiluted  condition.  The  gases  that  may  be  set  at  such 
examinations  are  included  in  the  following  list : — 


Acid  gases. 

Alkaline  gases. 

Neutral  gases, 

HCl. 

NH,. 

H2S. 

HNO3. 

(NHJ,S. 

cs,. 

N2O3,  etc. 

CO. 

Clo. 

soV 

CO,. 

NOXIOUS   GASES    IN   AIR  105 

Method  of  Procedure 

1.  Take  the  reaction  with  litmus  paper  which  has  been  made 

slightly  moist.  This  will  give  an  indication  whether  the 
gas  is  acid,  alkaline,  or  neutral. 

2.  Smell  the  gas.     Chlorine  and  hydrochloric  acid  gas  have  a 

characteristic  odour.  So  has  sulphur  dioxide.  Ammonia 
and  ammonium  sulphide  are  easily  distinguished,  the 
latter  giving,  besides  the  smell  of  ammonia,  the  un- 
pleasant odour  of  rotten  eggs.  Sulphuretted  hydrogen 
also  smells  like  these ;  and  carbon  disulphide  has  the 
odour  of  concentrated  bad  cabbages.  The  oxides  of 
nitrogen  have  their  own  particular  smell,  reminiscent  of 
strong  nitric  acid.  Carbon  monoxide  and  carbon  dioxide 
have  no  odour. 

With  these  aids  the  student  will  be  enabled  to  diagnose  that 
the  gas  he  is  examining  is,  at  the  most,  one  of  two  or  three.  He 
should  now  apply  confirmatory  tests,  as  follows  : — 

Dissolve  the  gas  by  shaking  in  10  c.c.  of  water,  and  test  the 
solution. 

HCl.  AgNOg  gives  a  white  precipitate  insoluble  in  HNO3,  ^^^ 

soluble  in  NH^OH. 
HNO3.  Brucine  test. 

N2O3  (now  HNOo).  Metaphenylene-diamine  test. 
Clo.  Bleaches  litmus  paper.     Moist  KI  paper  is  blackened  by 

the  liberation  of  free  iodine. 
SOo.  Characteristic   smell.     AgNOg    gives    a   white   precipitate 

soluble  in  HNO3. 
CO^.  Lime  water  or  Ba(OH)o  gives  turbidity. 
NH3.  Nessler's  reagent  gives  a  yellow-brown  colour. 
(NH^)2S.  Odour  characteristic.      Sodium  nitro-prusside  gives  a 

violet  colour. 
HgS.  Lead  acetate  paper  or  solution  is  darkened. 
CSo.  On  burning,  sulphur  is  deposited. 
CO".  Characteristic   colour  and   spectrum    when  shaken  with  a 

dilute  blood  solution. 


ANALYSIS  OF  SOIL 

The  chemical  and  physical  examinations  of  the  soil  are  attended 
by  many  and  great  difficulties,  and  the  training  necessary  to 
become  an  expert  in  the  subject  is  both  long  and  laborious. 
Fortunately  the  examinations  which  develop  upon  the  hygienist 
are  comparatively  simple. 

DETERMINATION   OF    THE   SIZE   OF    THE   PARTICLES 

A  series  of  sieves  is  taken,  having  meshes  of  2  mm.,  i  mm., 
and  o"5  mm.  respectively. 

100  grammes  of  air-dried  soil  is  taken  and  broken  as  finely  as 
possible  between  the  finger  and  thumb.  The  large  pebbles, 
sticks,  roots,  etc.,  are  removed  by  hand  and  weighed.  The 
remainder  is  next  transferred  to  the  2  mm.  sieve.  After  as  much 
of  the  soil  is  through  as  will  pass,  the  remainder  is  again  rubbed 
between  the  finger  and  thumb  in  order  to  break  up  any  cohering 
masses.  The  amount  left  on  this  sieve  is  then  weighed.  In  a 
similar  manner  the  amount  left  upon  the  other  sieves,  and  the 
amount  which  passes  the  0*5  mm.  sieve  is  weighed.  The  result  is 
then  tabulated  as  follows  : — 

1.  Coarse  pebbles,  etc.,  removed  by  hand. 

2.  Pebbles  and  coarse  sand  not  passing  a  2  mm.  sieve. 

3.  Sand  not  passing  a  i  mm.  sieve. 

4.  Fine  sand  not  passing  a  o  5  mm.  sieve. 

5.  Fine  earth  passing  a  0*5  mm.  sieve. 

DETERMINATION    OF  THE   MOISTURE 

Since  the  moisture-containing  property  of  the  soil  is  chiefly 
possessed  by  that  portion  of  the  soil  which  passes  a  2  mm.  sieve, 
5  grammes  of  such  air  dried  soil  are  carefully  weighed  in  a  tared 
dish.  The  dish  is  then  placed  in  a  water  oven  and  heated  for 
five  hours.  It  is  then  transferred  to  a  desiccator,  allowed  to  cool, 
and  weighed.  The  heating,  cooling,  and  weighing  are  repeated 
at  intervals  of  two  hours,  until  the  weight  is  found  to  be  constant. 
The  loss  in  weight  then  represents  the  moisture  in  5  grammes. 

106 


THE   POROSITY   OF   A   SOIL  107 

DETERMINATION    OF   THE    POROSITY   OF   A    SOIL 

The  porosity  of  a  soil  depends  upon  the  volume  of  the  sohd 
particles  as  compared  with  the  volume  of  the  interstitial  spaces. 
Three  factors  affect  the  porosity:  (i)  the  state  of  divisibility  or 
the  number  of  particles  per  unit  volume;  (2)  the  nature  and 
arrangement  of  these  particles  ;  and  (3)  the  interstitial  space. 

The  porosity  is  most  easily  determined  by  finding  the  real  and 
apparent  specific  gravity  of  the  soil  in  question,  and  dividing  the 
latter  by  the  former. 

The  real  specific  gravity  is  determined  by  means  of  a  pykno- 
meter  having  a  capacity  of  25  or  50  c.c.  10  grammes  of  soil  dried 
at  100°  C.  to  a  constant  weight  are  boiled  for  a  time  with  a  few 
c.c.  of  distilled  water  in  order  to  remove  any  air,  and  poured  into 
the  pyknometer.  The  vessel  is  rinsed  with  distilled  water,  so  that 
all  the  soil  is  transferred  to  the  pyknometer.  After  cooling  to  the 
requisite  temperature,  15°  C,  distilled  water  is  added  to  the  mark, 
and  the  whole  weighed.  The  weight  of  the  pyknometer  and  the 
pyknometer  filled  to  the  mark  with  water  being  known,  the  weight 
of  the  water  displaced  by  the  10  grammes  of  soil  is  easily 
obtained. 

Suppose  this  to  be  479 1. 

The  sp.  gr.  of  the  soil  is  then -p^  2*08. 

^    ^  5"io6 

The  apparent  specific  gravity  is  obtained  in  the  following 
manner  : — 

An  open  cylinder  holding  i  litre  is  taken  and  filled — small 
quantities  at  a  time — with  the  soil.  As  each  portion  is  placed 
in  the  cylinder,  the  bottom  is  struck  fairly  hard  with  the  palm  of 
the  hand.  When  the  cylinder  is  full  it  is  covered  with  a  glass 
plate  and  weighed.  The  weight  of  the  cylinder  and  plate  is 
deducted,  and  the  apparent  specific  gravity  thus  obtained. 

The  real  sp.  gr.  of  a  sample  of  soil  was  found  to  be  2*64,  and  the 

apparent  sp.  gr.  i  "28.  The  porosity  is  therefore  — ~-—  x  100  =  48*4%. 

2 '64 

Schiibler  gives  the  weights  of  different  kinds  of  soil  : — 


lbs.  per  cu.  ft. 
Sand       .         .         .110 
Sand  and  clay  .     96 

Common  arable  soil     80-90 


lbs.  per  cu.  ft. 
Heavy  clay      .         -75 
Vegetable  mould     .     78 
Peat        .         .         .     30-50 


The  specific  gravity  thus  decreases  as  the  amount  of  humus 
increases. 


io8  ANALYSIS   OF   SOIL 

ESTIMATION    OF   CLAY  AND   SAND 

The  constituents  of  soil  are  spoken  of  as  sand  and  clay,  the 
sand  being  the  coarser  particles  which  sink  rapidly  in  water,  the 
clay  being  the  very  fine  particles,  consisting  chiefly  of  silicate  of 
alumina,  which  remain  suspended  in  still  water  for  a  considerable 
time.  This  is  only  a  rough  division,  because  in  any  sample  of 
soil,  every  grade  can,  by  appropriate  methods,  be  found  between 
particles  3  mm.  in  diameter  and  particles  o'ooi  mm.  in  diameter. 

In  order  to  estimate  the  clay  and  sand,  10  grammes  of  air-dried 
soil  are  taken  and  placed  in  a  beaker  which  holds  about  200  c.c. 
The  soil  is  first  moistened  with  distilled  water  containing  o*oi% 
of  NH^Cl,  and  about  50  c.c.  or  100  c.c.  of  the  distilled  water  are 
added  and  the  soil  well  stirred.  The  soil  is  allowed  to  settle  for 
five  minutes  and  the  supernatant  fluid  poured  into  a  large  clean 
cylinder.  50  c.c.  or  100  c.c.  more  of  the  water  are  added, 
the  soil  well  mixed,  and  again  allowed  to  settle  for  five  minutes, 
when  the  supernatant  fluid  is  poured  off.  This  is  repeated  until 
the  supernatant  fluid  is  quite  clear. 

The  sand  remaining  in  the  beaker  is  transferred  on  to  a  filter 
and  well  washed  with  distilled  water,  dried,  weighed  and  returned 
as  sand. 

The  fluid  in  the  cylinder  is  allowed  to  stand  for  from  12  to  24 
hours,  when  the  clay  will  have  settled  at  the  bottom.  The  whole 
of  the  upper  part  of  the  fluid  is  filtered  through  filter-paper 
without  disturbing  the  sediment.  When  only  a  thin  layer  of 
water  is  left,  the  clay  is  stirred  up  and  transferred  to  the  filter- 
paper.  The  cylinder  is  well  rinsed  with  distilled  water  and  the 
washings  are  poured  on  to  the  filter-paper.  The  clay  is  then  well 
washed  (at  this  stage  filtration  is  so  slow  that  frequently  two  days 
are  required  to  complete  the  washing),  dried,  weighed,  and 
returned  as  clay. 

Good  loamy  soil  often  contains  from  10-15%  of  clay.  Stiff 
soils  contain  from  20-30%.  Sandy  soil  contains  only  i  or  2%, 
and  brick   clay   or  kaolin  contains  80-95%. 

DETERMINATION   OF   THE  SPECIFIC   HEAT  OF   SOILS 

The  specific  heat  of  any  substance  is  the  relation  between  the 
amount  of  heat  required  to  raise  a  given  mass  of  the  substance 
through  a  given  number  of  degrees,  and  the  amount  of  heat 
required  to  raise  the  same  mass  of  water  through  the  same 
number  of  degrees. 


NITRATES    IN    SOIL  109 

The  principle  involved  in  the  determination  is  that  a  certain 
mass  of  the  soil  heated,  say,  to  boiling  point  when  added  to 
water  at  a  certain  temperature  will  raise  the  temperature  of  the 
water  a  certain  number  of  degrees,  whereas  the  same  mass  of 
boihng  water  will  raise  the  temperature  a  different  number  of 
degrees.  As  the  operation  is  a  delicate  one  and  necessitates  the 
use  of  a  sensitive  calorimeter  it  hardly  lies  within  the  province  of 
this  book.  Suffice  it  to  say  that  there  is  a  very  considerable 
difference  in  the  specific  heats  of  various  soils. 

The  specific  heat  varies  from  o'iq  to  0-51,  the  latter  being  a 
peaty  soil.  Speaking  generally,  the  specific  heat  increases  with 
an  increase  of  humus  in  the  soil. 

ESTIMATION    OF   THE   ORGANIC    MATTER 

An  approximate  estimation  of  the  organic  matter  in  soil  may 
be  obtained  by  taking  10  grammes  of  air-dried  soil  and  heating  it 
in  a  platinum  dish  at  110°  C.  until  a  constant  weight  is  obtained. 
The  dish  is  then  transferred  to  an  Argand  burner  and  the  soil 
oxidized  at  a  low  red  heat.  When  the  oxidation  is  complete,  the 
dish  is  transferred  to  a  desiccator,  allowed  to  cool  and  weighed. 
The  loss  in  weight  gives  approximately  the  amount  of  organic 
matter. 

ESTIMATION   OF    NITRATES    IN    SOIL 

In  order  to  estimate  the  nitrates  and  nitrites  in  soil,  the 
sample  should  be  spread  in  a  thin  layer  in  an  oven  having  a 
temperature  of  5o''-6o°  C.  in  order  to  prevent  any  further 
nitrification. 

After  the  soil  is  dry,  1000  grammes  are  finely  powdered, 
weighed,  and  placed  in  a  large  flask.  2000  c.c.  of  distilled 
water  are  then  added,  well  mixed,  and  allowed  to  stand  (with 
frequent  shaking)  for  48  hours.  1000  c.c.  are  then  filtered.  A 
small  quantity  of  NagCOg  is  added  to  the  filtrate,  which  is  then 
evaporated  to  about  100  c.c. 

The  nitrates  are  then  estimated  by  the  phenol-sulphonic 
method. 


ANALYSIS    OF    GROUND    AIR 

In  order  to  collect  ground  air  for  analysis  a  convenient  method 
is  to  have  a  hollow  tube  furnished  with  a  steel  cone.  The  tube 
is  provided  at  its  lower  end  with  perforations,  and  when  it  has 
been  driven  into  the  ground  to  the  required  depth,  the  upper 
end  is  connected  with  an  aspirator  full  of  water ;  the  water  is 
allowed  to  flow  slowly  out.  When  the  necessary  amount  of  gas 
is  collected,  the  apparatus  is  transferred  to  the  laboratory  and  the 
gas  analysed. 

Ground  air  contains  about  the  normal  amount  of  nitrogen. 
The  COo  varies  from  i%  to  8%,  and  the  O2  is  correspondingly 
decreased.  From  time  to  time  NH3,  HoS,  CH^,  etc.,  are  found. 
The  methods  for  the  detection  of  the  first  two  will  suggest  them- 
selves to  the  student.  CH^  can  only  be  estimated  in  a  proper 
gas  apparatus,  which  is  somewhat  expensive,  and  which  requires 
special  practice  to  use. 


no 


DISINFECTANTS 

Certain  disinfectants  and  antiseptics  (boric  acid,  formalin,  and 
salicylic  acid)  have  already  been  discussed  in  the  chapter  on  milk 
analysis :  it  remains  now  to  consider  other  disinfectants  that  are 
not  usually  added  to  food  as  preservatives,  but  which  are 
employed  in  public  health  work  in  connection  with  the  control 
of  infection.  A  bacteriological  standard  is  here  obviously  of 
more  value  than  a  chemical  analysis ;  and  for  the  consideration 
of  the  Rideal- Walker  method  of  standardizing  disinfectants  the 
student  is  referred  to  text-books  on  bacteriology. 

Occasionally,  however,  the  D.P.H.  candidate  is  asked  to  identify 
some  disinfectant ;  and  possibly  to  determine  whether  the  sample 
submitted  to  him  has  been  adulterated  by  some  inert  substance : 
in  other  words,  he  is  required  to  estimate  the  quantity  of  the 
disinfectant  present  in  the  sample. 

BLEACHING   POWDER 

ESTIMATION    OF    AVAILABLE    CHLORINE 

Apparatus,  etc.,  required 

1.  A  flask  to  hold  i  litre. 

2.  A  burette  graduated  in  o'l  c.c. 

3.  A  solution  of  KI  in  water. 

4.  Freshly  prepared  starch  solution. 

N 

5.  —  Na2S203"5H20  (24-8  grammes  to  the  Htre). 

6.  A  porcelain  dish. 

The  Process 

1.  Weigh  out  10  grammes  of  the  bleaching  powder  and  transfer 

to  the  porcelain  dish. 

2.  Add  small  quantities  of  distilled  water   and  mix   with  the 

bleaching  powder  until  it   is  thoroughly  suspended  in  the 
liquid. 

Ill 


112  DISINFECTANTS 

3.  Transfer  the  liquid  to  the  litre  flask  and  wash  out  the  dish 

with  more  distilled  water.     Transfer  this  to  the  litre  flask 
and  make  up  to  i  Utre  with  distilled  water. 

4.  Shake  the  flask  thoroughly. 

5.  Measure  20  c.c.  of  the  solution  into  a  dish  and  dilute  with 

about  50  c.c.  of  distilled  water. 

6.  Add  a  drop  of  acetic  acid,  and  excess  of  KI  to  the  bleaching 

powder  solution  in  the  dish.     Free  iodine  will  be  liberated 
in  proportion  to  the  amount  of  available  chlorine. 

7.  Estimate  the  iodine  by  means  of  the  decinormal  thiosulphate 

solution,    judging  the   end  point    more   accurately  by  the 
addition  of  some  of  the  starch  solution. 

Explanation 

Bleaching  powder  consists  of  a  number  of  compounds ;  the 
one,  however,  which  gives  rise  to  the  available  chlorine  probably 
has  the  formula  CaOClg-  This  in  contact  with  water  and  a 
dilute  acid  liberates  free  chlorine. 

CaOClj  +  H2O  =  Ca(0H)2  +  Clg 

The  chlorine  in  the  presence  of  KI  liberates  free  iodine. 

2KI  +  Cl2=2KCl  +  l2 

This  iodine,  and  so  the  chlorine,  is  estimated  directly  by  the 
decinormal  thiosulphate  solution. 

Notes 

The  thiosulphate  solution  should  be  freshly  prepared. 
A  good  bleaching  powder  will  give  as  much  as  33%  of  available 
chlorine. 

CARBOLIC  ACID   (PHENOL) 

Qualitative  Tests 

1.  Ferric  chloride  gives  a  deep  violet  colour  with  a  solution  of 

phenol. 

2.  Bromine  water  gives  with  phenol  a  white  crystalline  precipitate 

of  tri-bromo-phenol. 

3.  KNO2  and  strong  HgSO^  gives  a  brown  colour,  changing  to 

green  and  blue. 

ESTIMATION   OF   PHENOL 

TRI-BROMO-PHENOL   METHOD 

Apparatus,  etc.,  required 

1.  Two  stoppered  flasks,  each  of  about  150  c.c.  capacity. 

2.  500  c.c.  flask. 


ESTIMATION    OF   PHENOL  113 

3.  Graduated  pipettes — 25  c.c.  and  5  c.c. 

4.  Solution  of  KI  in  water. 

5.  Solution  of  sodium  thiosulphate  (10  grammes  to  the  litre). 

6.  Standard  solution  of  NaBr  and  NaBrOg  (i    c.c.  =0-0012638 

grammes  of  phenol). 

7.  Starch  solution. 

8.  Graduated  burette. 

The  Process 

1.  Weigh  out  I  gramme  of  the  sample  phenol  and  dissolve  in  500 

c.c.  of  distilled  water,  to  which  a  trace  of  NaOH  has  been 
added  to  facilitate  the  solution. 

2.  Take    25    c.c.    of  this    solution    and  transfer  to    one  of  the 

stoppered  flasks.  To  the  same  flask  add  25  c.c.  of  the 
standard  bromine  solution  and  5  c.c.  of  pure  HCl.  Bro- 
mine will  be  liberated. 

3.  Stopper  the  flask. 

4.  To  the    control  flask  add   25   c.c.   of  the  standard  bromine 

solution  and  5  c.c.  of  pure  HCl.  Bromine  will  be  liberated. 
Stopper  the  flask. 

5.  To  each  flask  add  excess  of  the  KI  solution.    The  free  bromine 

will  combine  with  the  KI  and  iodine  will  be  liberated. 

6.  From  the  burette  run  the  thiosulphate  into  the  control  flask 

until  the  colour  has  disappeared.  Add  a  little  starch 
solution  as  in  the  estimation  of  available  chlorine.  A  few 
c.c.  of  chloroform  added  to  the  contents  of  the  flask 
sharpens  the  reaction.  Note  the  number  of  c.c.  of  thio- 
sulphate used. 

7.  Add  thiosulphate  solution  similarly  to  the  flask  containing  the 

sample  phenol,  until  all  the  colour  is  discharged.  Note  the 
amount  of  thiosulphate  solution  used. 

Explanation 

The  standard  solution  containing-  NaBr  and  NaBrO.>  liberates 

.  .  .  "-* 

free  bromine  on  the  addition  of  an  acid. 

SNaBr  +  NaBrOg  +  6HC1  =  6NaCl  +  3H2O  +  3Bro 
The  free  bromine  thus  liberated  combines    with  the  phenol 
present  to  form  tri-brorno-phenol. 

The  amount  of  bromine  used  up  by  the  phenol  is  represented 
by  the  difference  in  the  amounts  of  thiosulphate  solution  required 
respectively  by  the  control  and  by  the  sample  solutions.     Know- 
ing the  amount  of  bromine  used  up  in   converting  the  phenol 
8 


114  DISINFECTANTS 

into  tri-bromo-phenol,  the  percentage  of  phenol  actually  present 
in  the  sample  can  be  easily  determined. 

EXAMPLE 

The  control  flask  required  20*3  c.c,  of  thiosulphate  solution  to 
decolourize  its  contents. 

The  flask  containing  the  sample  required  8 "6  c.c.  of  thio- 
sulphate solution. 

.'.  the  phenol  in  the  sample  absorbed  bromine  corresponding 
to  20*3- 8  6  c.c.  of  thiosulphate  solution,  or  11  "9  c.c. 

Now  2o*3  c.c.  of  thiosulphate  solution  =  25  c.c.  of  the  standard 
bromine  solution 

.'.  1 1 '9  c.c.  of  thiosulphate  solution  =  25  x  11 '9 

20-3 
=  i4'65  c.c.  of  standard  solution. 

But  I  c.c.  of  the  standard  solution  =  0*0012638  grammes  of 
phenol 

.'.  14*65  c.c.  of  the  standard  solution  =  0*01851  grammes  of 
phenol. 

.*.  in  25  c.c.  of  the  sample  there  were  0*01851  grammes  of 
phenol. 

.*.  in  500  c.c.  of  the  sample  there  were  0*37  grammes  of 
phenol. 

Therefore  in  the  gramme  of  the  sample  of  phenol  there  was 
present  but  little  more  than  a  third  of  pure  phenol. 

Notes 

The  flasks  should  be  kept  stoppered  as  much  as  possible,  in 
order  to  prevent  the  escape  of  any  bromine  vapour. 

The  standard  bromine  solution  has  the  following  composition : 
Sodium  bromide  8*0  grammes,  sodium  bromate  2*04  grammes. 
Distilled  water  to  i  litre,  i  c.c.  of  this  solution  is  equivalent  to 
0*0012638  grammes  of  phenol. 

Potassium  or  sodium  permanganate  is  used  sometimes  as  a  dis- 
infectant. It  is  easily  recognized  from  its  colour.  When  an 
acid  solution  of  oxalic  acid  is  added  the  colour  disappears.  The 
strength  of  a  permanganate  solution  can  be  estimated  by  means 
of  decinormal  oxalic  acid  in  the  presence  of  H.^SO^. 

Copper  sulphate  and  zinc  chloride  and  salts  of  iron  are  used 
occasionally  for  their  disinfecting  properties.     The  detection  of 


ESTIMATION    OF   PHENOL  115 

these  metals  has  already  been  considered  in  the  section  devoted 
to  water  analysis. 

Sulphites  and  sulphurous  acid  are  not  used  on  a  large  scale 
for  disinfection  except  when  SOg  is  used  for  fumigating  rooms. 
The  smell  of  SOg  and  of  sulphurous  acid  is  characteristic. 

Salicylic  acid,  boric  acid,  and  formalin  have  been  referred  to 
in  the  chapter  on  milk  analysis. 

Beiizoic  acid  is  too  expensive  to  use  on  a  large  scale.  It  is 
occasionally  found  in  foods.  FcoClg  gives  a  red  precipitate. 
When  heated  with  lime  benzine  is  evolved. 

Mercuric  chloride  and  the  other  salts  of  mercury  have  all  dis- 
infectant properties.  H^S  gives  a  black  precipitate  with  mercuric 
solutions,  and  KOH  gives  a  yellow  precipitate  of  HgO.  On 
placing  copper  foil  in  a  solution  of  a  mercury  salt  the  mercury  is 
deposited  on  the  copper. 


MICROSCOPY 

This  part  of  the  book  deals  with  the  microscopical  examination 
of  food,  clothing,  parasites,  water  sediment,  etc.,  and  includes 
descriptions  of  all  the  microscopical  material  about  which 
a  D.P.H.  candidate  is  likely  to  be  questioned  in  his  examination. 

No  pretence  is  made  that  this  section  is  a  complete  treatise  on 
such  a  vast  subject  as  parasitology,  and  if  the  student  wishes  for 
more  minute  descriptions  he  is  recommended  to  consult  one  of 
the  many  text-books  on  that  science.  For  the  ordinary  D.P.H. 
candidate,  however,  the  subject  matter  in  this  part  of  the  book 
will  be  found  amply  sufficient. 

It  is  almost  impossible  to  follow  a  routine  plan  in  the  arrange- 
ment of  this  section  ;  but,  as  far  as  possible,  the  subjects  have 
been  kept  together  :  for  instance,  the  parasites  of  wheat  are  dealt 
with  in  connection  with  wheat,  rather  than  with  the  other  parasites. 

FOOD 

EXAMINATION  OF  STARCHES 
METHODS  OF  MOUNTING 

A.  In  Water 

1.  Clean  a  slide  with  a  handkerchief  and  see  that  it  is  dry. 

2.  With  a  clean  platinum  loop  remove  a  small  quantity  of  the 

starch  to  be  examined,  and  place  it  in  the  centre  of  the  slide. 

3.  Take  the  slide  in  one  hand,  holding  it  by  one  end,  and  tap  the 

opposite  end  against  the  desk,  and  remove  all  the  starch 
which  does  not  readily  adhere  to  the  shde. 

4.  By  means  of  the  sterilized  loop  place  three  or  four  loopfuls  of 

water  in  the  centre  of  the  slide  and  mix  the  starch  well. 

5.  Breathe  on  a  clean  coverslip  and  whilst  the  surface  is  moist 

with  the  condensed  water,   gently  drop  it — moist  surface 
downwards — on  to  the  mixture  of  starch  and  water. 

6.  If  the  water  runs  out   round   the  coverslip  remove  the  excess 

with  a  little  filter-paper.     The  preparation  is  now  ready  to 
be  examined. 

116 


FOOD  117 


B.  In  Dilute  Iodine  Solution 

This  method  is  a  very  useful  one,  as  the  concentric  rings  can 
very  often  be  seen  with  great  distinctness,  even  in  specimens 
which  only  show  them  faintly  when  mounted  in  water. 

The  process  of  mounting  is  identical  with  that  above  described, 
a  weak  solution  of  iodine  being  used  instead  of  water. 

The  solution  of  iodine  recommended  is 

Gram's  iodine    .         .         .         .     i  part. 
Water         .         .         .         .         .     3  or  4  parts. 

These  specimens  prepared  in  either  of  the  above  ways  will 
only  last  as  long  as  the  water  remains.  In  the  warm  laboratory 
they  very  soon  dry.  For  this  reason,  they  should  be  examined  as 
soon  as  prepared,  and  if  sketches  are  to  be  made,  they  should  be 
made  at  once. 

C  In  Farrant's  Solution 

Proceed  as  in  A^  omitting,  however,  to  breathe  on  the  cover- 
slip. 

Mounted  in  this  way,  starches  will  keep  for  two  or  three 
weeks. 

The  starch  granules  possess  certain  characteristic  appearances 
either  in  their  size,  shape,  concentric  rings  or  hila.  These 
appearances  enable  us  to  divide  them  into  live  groups. 

It  is  not  always  easy  to  differentiate  from  one  another  starches 
in  the  same  group  ;  but  not  difficult  to  determine  into  which 
group  a  starch  should  be  placed. 


GROUP   I 

Wheat,  Barley,  Rye 

The  granules  in  this  group  are  circular  or  oval  in  appearance, 
some  being  large  and  others  small.  They  have  no  very  apparent 
hilum  and  no  concentric  rings. 

1.  Wheat  {Tritiaim  viilgare). 

2.  Barley  {Ho?'deum  vtilgaj-e). 

3.  Rye  {Secale  ce?'eak). 


ii8  MICROSCOPY 


O 


^o°        ©0^     ^° 


FIG.  2  FIG.  3  FIG.  4 

WHEAT  STARCH         BARLEY  STARCH         RYE  STARCH 

X     200  X     200  X     20O 

1.  The  wheat  granules  are  generally  very    perfect.     They  are 

chiefly  of  two  sizes,  large  ones  varying  in  shape  from 
circular  to  oval,  and  very  small  ones.  Sizes  intermediate 
between  these  are  rare. 

2.  The  granules  of  barley  resemble  those  of  wheat,  but  (i)  the 

large  granules  are  more  circular,  (2)  the  number  of  inter- 
mediate sizes  is  proportionally  much  greater,  and  (3)  sHght 
indications  of  concentric  rings  may  be  seen. 

3.  The  granules  of  rye  resemble  the  two  preceding  ones,  but  (i) 

the  large  granules  are  larger  than  either  wheat  or  barley, 
(2)  the  large,  intermediate,  and  small  granules  are  more 
nearly  equal  in  number,  (3)  the  granules  are  more  frequently 
cracked  and  occasionally  show  a  stellate  hilum  but  no  con- 
centric rings. 

GROUP   II 

Potato,  Arrowroot 

The  granules  of  this  group  are  large  and  oval,  and  show  a 
distinct  hilum  and  well-marked  concentric  rings. 

1.  Potato  (So/amiPi  tuberosum). 

2.  Arrowroot  {Marania  arundinaced). 

1.  The  potato  granules  have  the  hilum  as  a  point  at  the  narrow 

end. 

2.  The  arrowroot  granules,  on  the  other  hand,  have  a  punctate 

or  linear  hilum  at  the  broad  end. 


FOOD 


119 


Note 

Although  it  is   not  true    that    every   potato  granule  has    the 
hilum   at  the   narrow  end,   or  is  even  oviform ;  or  that    every 


FIG.  5. 


rOTATO   STARCH 
X    200 


FIG.    6. 


ARROWROOT  STARCH 

X    200 


arrowroot  granule  has  the  hilum  at  the  broad  end ;  the  majority 
of  the  granules  in  any  pure  specimen  agree  with  this  description. 
It  would  be  obviously  impossible  to  differentiate  between  one 
oval  potato  and  one  oval  arrowroot  granule. 


GROUP   III 

Pea,  Bean,  Maize 

The  granules   of  this  group   are  round  or  oval  without  any 
evident  rings,  but  with  linear  or  stellate  hila. 

1.  Pea  [Fitsum  sativum). 

2.  Bean  {Faba  vulgaris). 

3.  Maize  {^Lea  mays). 


FIG.   7.      PEA  STARCH 
X    200 


FIG.  8.     BEAN  STARCH 
X    200 


FIG.  9.      MAIZE  STARCH 
X    200 


I.  The  pea  granules  are  generally  a  long  oval  in  shape,  fairly 
large,  but  showing  different  sizes.  They  generally  present  a 
linear  hilum,  but  this  is  sometimes  branched. 


I20  MICROSCOPY 

2.  The  bean  granules  are  of  a  shorter  oval  than  those  of  the  pea, 

and  are  more  uniform  in  size.  The  hilum  is  linear,  but 
more  often  branched  (sometimes  even  stellate)  than  in  the 
case  of  pea  granules. 

3.  The  maize  granules  are  mostly  polyhedral  in  shape — approxi- 

mating to  the  oval  form.  They  are  often  cracked,  and 
present  a  well-marked  stellate  hilum. 


GROUP   IV 

Rice,  Oats 

The  granules  of  this  group  are  much  smaller  than  those  of  the 
preceding  groups.    They  are  angular,  and  appear  to  be  faceted. 

1.  Rice  {Oryza  sativd). 

2.  Oat  {Avena  sativd). 

1.  The    rice    granules    are    the         Q      ^ 

smallest  of   all  those   with        n   ^  =q  ^ 

which weare  dealing.  Under        ^  O       <;;i 

a  higher  power  an  eccentric  rvr':;^^ 

hilum    may    sometimes    be  /fc^'':^; 

made    out.      The    granules  ^j^h^-r-^- 

are   often   massed    together  ^     '^^ 

in     angular     and     irregular  ^^^*  ^*^  ^'^'  ^^ 

°  °  RICE  STARCH  OAT  STARCH 

shapes.  x  200  x  200 

2.  The  oat  granules  are   larger 

than  those  of  rice,  and  hila  are  not  to  be  found.  These 
granules  are  found  in  masses,  but  the  contour  is  generally 
regular  and  oval,  and  not  irregular  and  angular. 


GROUP   V 

Sago,  Tapioca 

The  granules  of  this  group  are  very  irregular  in  shape,  and 
many  appear  truncated.  They  have  a  hilum  and  badly  defined 
rings. 

1.  Sago  i^Sagus  fa7-iniferd). 

2.  Tapioca  (^Jatropha  manihot). 


ANIMAL   PARASITES 


121 


The  sago  granules  are  large 
and  irregular.  They  are 
often  rounded  at  one  end 
and  truncated  at  the  other. 
The  hilum  is  frequently 
rounded. 

The  tapioca  granules  are 
much  smaller  than  those 
of  sago,  but  are  in  other 
respects  similar. 


(^ 


FIG.    12 
SAGO  STARCH 

X  200 


FIG.    13 

TAPIOCA  STARCH 

X  200 


The  Parasites  of  Grain,  Flour,  etc. 

Various  parasites  are  found  affecting  grains,  flours,  and  bread. 
Some  of  these  parasites  are  harmless,  others  are  somewhat 
injurious  when  consumed. 

They  may  be  divided  into  two  classes  : — 

1.  Animal. 

2.  Vegetable. 

I.  ANIMAL  PARASITES 

a.  Corn  weevil  ( Calandra  granaria), 

b.  Meal  mite  {Acarus  farince). 

c.  Pea  biuchus  {Bruchus  pisi). 

d.  Ear  cockle  {Tylenchus  tritict). 

a.  The  Calandra  granaria  is  one  of  many  allied  species  of 

insect  which  affect  grain. 

The  corn  weevils  belong  to  the  order 

of  Beetles  (Coleoptera).    Two  species  are 

well    known   in   England,  the    Calandra 

granaria    (or    Sitophilus  granarius)   and 

the  Sitophilus 
oryzce. 

The  insect 
perforates  the  shell  and  abstracts  the 
contents  of  the  seed,  leaving  merely 
the  coverings.  All  the  harm  this  in- 
sect does,  therefore,  is  simply  to  eat 
the  flour  ;  it  does  not  of  course  affect 
any  grains  which  are  not  attacked, 
nor  is  it  ground  up  with  the  flour  as 


FIG.  14 

CALANDRA  GRANARIA 

X  4 


FIG.   15. 
X  100. 


ACARUS  FARIN/E 
{adnai.  T.G.S.) 


122 


MICROSCOPY 


in  the  case  of  some  of  the  parasites.     The  grains  are  attacked 
when  the  corn  is  actually  standing. 

b.  Acarus  farince.  This  is  also  an  insect  which  is  frequently 
found  in  inferior  and  damp  meal,  flour,  etc. 

It  bears  some  resemblance  to  the  Acai'us  scabei,  but  a  close  examination 
will  reveal  the  great  difference  between  the  bodies  and  legs.  The  body  of  the 
Acarics  scabei  is  much  rounder  than  that  of  the  farinK,  and  the  legs  of  the 
meal  mite  are  fairly  thick  up  to  the  extremity,  whilst  those  of  the  Acarus 
scabei  are  thick  at  the  proximal,  but  quite  thin  at  the  distal  end. 

c.  The  Bruchus  pi  si.  The  Bruchus  pisi  (the  pea  bruchus), 
Bruchus  rufimajius  (bean  bruchus),  and  the  Bruchus  granarius 

(the  grain  bruchus)  belong  to  the  same 
order  (Coleoptera)  as  the  weevils,  which 
they  resemble  in  their  main  features.  The 
first  two,  as  their  names  imply,  are  con- 
nected with  peas  and  beans.  The  adult 
female  lays  her  eggs  in  the  young  fruit,  and 
the  larvae  live  in  the  seeds,  eating  up  all 
the  internal  parts  and  changing  to  pupse 
FIG.  i6.    BRUCHUS  PISI  ^jthin  thc  outcr  shell. 

d.  The  Tylenclius  tritici  ( Vi'dn'o  tritici). 
The  worms  seen  when  the  contents  of  an  infected  grain  are 
examined  under  the  microscope 
are  the  larval  forms  of  a  nema- 
tode worm. 

In  the  ears  of  wheat  affected 
by  this  worm  the  grains  are  mis- 
shapen, blackish,  and  consist  of 
a  thick  hard  scale  enclosing  a 
white  powdery  substance,  com- 
posed almost  entirely  of  the 
larval  forms  of  the  worm. 

In  order  to  examine  this 
powder  under  the  microscope, 
it  is  only  necessary  to  place  a 
little  on  a  clean  slide  and  to 
mount  it  in  water. 

Permanent  specimens  may  be 
prepared  by  mounting  in  Farrant's  solution,  the  powder  may  be 
thoroughly  dehydrated  by  drying  or  by  treatment  with  alcohol 
and  xylol,  and  mounted  in  Canada  balsam.     Very  pretty  speci- 


FIG.    17.       TYLENCIIUS  TRITICI 
X  60.     {ad  flat.  T.G.S.) 


VEGETABLE   PARASITES 


123 


mens  may  be  prepared  by  staining  the  worms  with  eosin  and 
mounting  in  Canada  balsam,  in  the  usual  manner. 

If  the  infected  grain  be  sown  in  ordinary  moist  ground,  the 
husk  simply  rots.  The  larvae  escape  and  become  active.  They 
move  along  the  ground  in  search  of  growing  blades  of  corn. 
When  they  find  one,  they  slowly  creep  up  and  eventually  reach 
the  young  soft  grain,  which  they  penetrate.  Here  they  form  gall- 
like swellings,  in  the  middle  of  which  they  are  found. 

In  this  position  they  quickly  develop  into  the  adult  form. 
After  fertilization  by  the  males,  the  females  lay  a  large  number  of 
eggs,  and  both  males  and  females  die.  The  eggs  subsequently 
hatch  and  the  larvae  are  seen. 

Closely  allied  to  this  worm  is  the  Angiiilliila  aceti^  which  is 
sometimes  found  in  vinegar,  when  this  is  made  from  beer  or  wine, 
and  which  is  also  found  in  sour  paste. 

II.  VEGETABLE   PARASITES 

a.  rejiicillium  glaucum. 

b.  Aspergillus  glaucus,  albus^  etc. 

c.  Miicor. 

d.  Peronosporon. 

e.  Piiccinia  graminis  and  Riibigo  vera  (rust). 
/    Ustilago  segetum  (smut). 

g.    Tilletia  caries  (bunt,  Uredo  foiHda,  Ustilago  carbd). 
h.   Claviceps  purpurea  (ergot). 

a.  The  PenicHUum  glaucum  is  a  common  mould,  found  very 
extensively  in  the  air.     It  is  frequently 
found   forming   a    greenish    growth,    on 
damp  grain,  flour,  bread,  or  cheese. 

This  mould  resembles  the  others  in 
consisting  of  many  long  threads  (hyphae) 
often  interlaced  and  forming  a  mycelium. 
The  hyphae  branch  and  produce  special 
spore-bearing  ones.  The  end  of  this  last 
hypha  then  branches  into  three  or  more 
terminal  filaments  which  in  their  turn 
divide  transversely  to  the  long  axis.  The 
protoplasm  of  these  short  rods  now  be- 
comes differentiated  and  round  or  oval 
spores  with  thick  cell  walls  are  found. 
These  soon  separate  from  one  another,  fjq    ^ 

and  free  spores  are  found.  penicillium  glaucum 

X    100 


124 


MICROSCOPY 


b.  Aspergillus  glaucus,  etc.  This  species  of  mould  is  also 
found  in  damp  grain,  etc.  It  resembles  the  penicillium 
in  its  mode  of  growth,  but  differs  from  it  in  the  way 
in  which  the  spores  are  formed.  The  end  of  the 
spore-bearing  hypha  becomes  enlarged  and  the  spores 
appear  to  grow  out  of  the  bulbous  end,  and  are  at 
first  attached  to  it  by  fine  pedicles.  Generally  there 
are  two  or  three  rows  of  spores  on  each  head,  the 
pedicles  of  the  external  row  being  longer  than  those 
of  the  other  rows.  When  the  spores  are  ripe  they 
simply  fall  off,  and  so  become  free. 

c.  Mucor.  This  form  of  mould  is  found  in  similar 
positions  to  the  last  two.  It  resembles  these  in  its 
mode  of  growth  except  that  it  forms  its  spores  in  still 
another  way.  The  end  of  the  spore-bearing  hypha 
becomes  enlarged,  and  instead  of  the  spores  growing 
out  from  this  enlargement,  as  in  the  case  of  the 
aspergillus,  the  end  attains  a  considerable  size  (quite  visible  to 
the  naked  eye).     The  protoplasm  within  the  wall  of  the  head 


FIG.  19 

ASPERGILLUS 

X  100 
(After  Howes) 


FIG.   20.     MucoR  :  {a)  special  spore-l:)earing  hyplice  ;  {d)  head  x  100, 
showing  internal  spores  ;  (t)  and  {d)  conjugation.    (After  Howes) 

undergoes  differentiation,  and  the  spores  are  formed  by  this  means 
inside  the  envelope  which  surrounds  the  head.  When  the  spores 
are  ripe  the  envelope  is  ruptured,  and  the  spores  set  free. 


VEGETABLE    PARASITES 


125 


This  mould  is  occasionally  found  to  multiply  by  a  process  of 
conjugation,  as  shown  in  the  diagram.  The  swelling  so  formed 
is  found  to  become  differentiated  in  a  manner  similar  to  that 
found  in  the  head  produced  on  a  hypha. 

d.  Peronospora.  These  moulds  do  not  affect  the  prepared 
product  so  much  as  the  living  plant.  They 
were  the  cause  of  the  great  Irish  potato 
famine,  and  are  found  affecting  many  of 
the  "  root "  crops  as  onions,  parsnips, 
turnips,  etc. 

The  mould  first  affects  the  leaves  and 
gradually  travels  downwards  until  finally 
the  tuber  or  root  is  affected. 

The  growth  consists  of  a  dense  mycelium 
which  produces  spore-bearing  hyphre  ex- 
ternally. 

These  hyphce  frequently  branch,  some- 
times many  times.  At  the  end  of  each 
branch  a  single  spore  is  produced.  This 
when  it  is  ripe  separates  and  so  becomes 
free. 

e.  Puccinia  gramini's.  This  parasite 
is  found  affecting  many  varieties  of  corn. 
The  process  of  infection  is  as  follows  :  A  spore  becomes  attached 
to  the,  say,  wheat  grain,  and  as  it  grows,  it  sends  free  filaments 
into  the  interior  of  the  grain.  As  time  goes  on  minute  trans- 
parent cellules  are  developed  from  the  mycelium  :  these  enlarge 
and  become  coloured.     As  the  result  of  their  increase  in  size, 

the  cuticle  first  becomes  distended, 
and  finally  ruptures,  and  the  spores 
are  found  at  the  surface  as  rust. 

The  distinctive  features  of  the 
Puccinia  are  the  uniseptate  or 
double  spores,  which  are  attached 
on  a  distinct  peduncle,  and  it  is 
in  this  condition  that  the  parasite 
is  shown  at  the  various  examin- 
ations. 

/    Ustilago     segetum     (syn. 

Uredo   segetufii,    smut).      This — a 

-is  one  of  a  large  family  of  parasites 


FIG.   21.      PERONOSPORON 
X  100.     (After  Vines) 


■309 


^^Xo^ospSf^ 


Fig.  22 
spores  of  puccinia  gramims 
X  350 


common  parasite  of  corn- 
which  are  found  affecting  plants. 


126 


MICROSCOPY 


FIG.   23 

USTILAGO 

SEGETUM 

X  500 


Among  the  standing  com  withered  heads  are  often 
seen,  which  appear  black  or  brown.  If  they  are  rubbed, 
or  even  touched,  a  fine  brownish  powder  falls  off.  This 
powder  consists  of  the  spores  of  the  parasite. 

Under  the  microscope  these  are  seen  to  be  small 

spherical  spores,  which  are  generally  coloured  a  light 

brown.     They  are  entirely  free,  as   by  the  time  the 

spores  are  ripe  the  mycelium  will  have  disappeared. 

,^.    Tilletia  caries  (syn.    Uredo  f(Etida,    Ustilago  carho,  bunt). 

This  is  another  member  of  the  ustilagime,  to  which  order  the 

Ustilago  segetum  belongs. 

The  parasite  is  found  in  the  interior  of  the  grain,  but  does 
not  affect  its  external  appearance,  or  if  it  does  only  by  slightly 
darkening  it.  In  fact  it  is  often  stored  with  the  sound  grain,  and 
it  is  not  until  the  corn  is  ground  that  its  presence  is  determined. 

If  an  affected  grain  be  cut  or  broken  open,  the  interior  is  seen 
to  be  filled  with  a  sooty,  rather  fetid  powder.  When  this  powder 
is  rubbed  between  the  fingers  it  has  a  greasy  feel. 

Under  the  microscope  these  spores  are  seen  to  be  brownish 
spherical  bodies  with  a  reticulated  surface.  They  are  generally 
free,  but  some  are  found  with  part  of  the  attached  hyphae,  and 
sometimes  two  or  three  are  seen  to  be  joined  together  by  hyphae. 


FIG.    24.       TILLETIA   CARIES 
X  200.    {ad  nat.  T.G.S.) 


FIG.  25.     TILLETIA   CARIES 
X  500.    {ad nat,  T.G.S.) 


h.  G/auiceps  purpurea.  This  fungus  is  found  chiefly  affect- 
ing rye,  and  the  mycelial  growth — termed  the  sclerotium — which 
replaces  the  actual  grain  is  known  as  ergot.  In  the  spring  time 
of  the  year  small  hair-like  growths  with  a  bulb  at  the  end  grow 
out  from  the  mycelium.  These  are  known  as  stromata,  and  each 
contains  near  its  border  a  row  of  receptacles  (ascocarps),  contain- 
ing oval-shaped  bodies  known  as  asci.     These  ascocarps  and  the 


MILK 


127 


contained  asci  are  the  preparations  of  ergot  usually  shown  at  the 
examinations. 

CLAVICEPS   PURPUREA 
(ergot  of  rye) 


FIG.  26.       SCLEROTIUM  FIG.  27.       SECTION  OF  THE  END  OF  A 

WITH  STROMATA  STROMA,  SHOWING  ASCOCARPS  AND  ASCI 

(Nat.  size)  X  80.    (Photo) 

MILK 

The  microscopical  examination  of  milk,  apart  from  bacterio- 
logical considerations,  is  not  of  great  value  in  hygiene.  Pure 
normal  milk  when  viewed  with  the  microscope  is  seen  to  consist 
almost  entirely  of  fat  globules,  which  vary  only  slightly  in  size. 
The  globules  are  all  small,  the  largest  being  about  three  times 
the  size  of  the  smallest.  In  many  samples  of  pure  milk  cellular 
elements  are  absent  or  rare  ;  but  in  others  obtained  from  un- 
doubtedly pure  sources  "  leucocytes  "  may  be  present,  sometimes 
in  large  numbers.  These  leucocytes  closely  resemble  poly- 
morphonuclear leucocytes,  but  differ  from  them  in  slight  respects  : 
their  presence  alone  is  not  sufficient  to  condemn  a  milk  sample. 
If,  however,  typical  polymorphonuclear  leucocytes  are  seen, 
accompanied  by  pyogenic  organisms,  the  milk  may  be  from  a 
cow  suffering  from  mastitis  and  then  will  be  unfitted  for  human 
consumption. 

Gross  dirt,  such  as  manure,  hairs,  shreds  of  clothing,  etc.,  will 
also  render  a  milk  sample  unfit  to  drink ;  and  shows  neglect  on 
the  part  of  the  provider  to  filter  the  milk  before  it  was  dis- 
tributed. 


128 


MICROSCOPY 


BUTTER  AND   MARGARINE 

Although  the  microscopic  examination  of  butter  and  margarine 
is  not  so  important  as  the  chemical  examination,  pure  butter 
differs  very  markedly  from  margarine. 

In  order  to  examine  these  substances,  a  small  quantity  of  the 
butter  or  margarine  should  be  spread  in  a  thin  layer  on  a  clean 
slide.     A  drop  of  i  %  osmic  acid  in  water  should  then  be  placed 


FIG.  28.       BUTTER 
X  400.    {adnat.  T.G.S.) 


VIG.  29.       MARGARINE 
X400.    {ai{  nat.  'J'.G.S.) 


on  the  fat  and  a  clean  coverslip  superimposed.  The  osmic  acid 
serves  to  show  the  contour  of  the  globules  very  clearly. 

In  the  case  of  pure  butter  it  will  be  seen  that  the  globules  are 
small  and  do  not  vary  much  in  size.  The  largest  globules  are  not 
more  than  four  or  five  times  the  size  of  the  smaller  ones. 

The  globules  of  margarine  vary  greatly  in  size,  the  largest  being 
fifteen  to  twenty  times  as  large  as  the  smallest  ones. 

COFFEE 

Coffee  is  obtained  from  the  seeds  of  the  Cnffea  Arabica.  For 
use  it  is  ground  and  generally  mixed  with  a  modicum  of  chicory, 
varying  from  10  to  90%.  So  long  as  such  a  mixture  is  sold  as  a 
mixture  there  is  no  infringement  of  either  law  or  honesty.  It 
sometimes  happens,  however,  that  a  mixture  of  ground  coffee  and 
chicory  is  sold  as  pure  coffee.  In  order  to  detect  this  fraud  it  is 
necessary  to  be  able  to  identify  the  two  substances. 

In  order  to  examine  them  under  the  microscope  the  ground 
substances  should  be  warmed  in  a  watchglass  containing  40% 


COFFEE 


129 


soda  solution,  and  mounted  in  water  or  soda.  Unless  this  is 
done  it  will  be  found  that  the  grains  are  so  hard  and  coarse  that 
it  will  be  impossible  to  mount  them  satisfactorily.     The  soda  will 


FIG.   30.       MEMBRANE  OF  COFFEE  BERRV,  SFIGWING  SPINDLE  CELLS 
X  100.     (ad  naL  T.G.S.) 

take  some  of  the  colour  out  of  the  grains,  but  this  will  be  found 
an  advantage  rather  than  a  disadvantage. 

Under  the  microscope  the  endosperm  cells  form  the  main  bulk 


FIG.  31  FIG.  32 

DOTTED  VESSELS  OF  CHICORY       LACTEAL  VESSELS  OF  CHICORY 
X  100.    (After  Moller)  X  100.    (After  MOller) 


130 


MICROSCOPY 


of  the  preparation.  These  are  knotted,  thickened,  thick-edged 
and  polygonal,  and  may  contain  remnants  of  the  original  con- 
tents. Here  and  there  will  be  found  remnants  of  the  membrane 
lining  the  berry.  This  membrane  has  attached  to  it  a  number  of 
very  characteristic  spindle-shaped  cells. 

Chicory  consists  of  the  ground  dried  root  and  contains 
elements  quite  foreign  to  the  coffee  berry.  The  parenchyma  is 
much  more  open  than  the  endosperm  cells,  and  both  lacteal 
vessels  and  the  dotted  ducts  are  numerous. 

Numerous  other  adulterants  are  from  time  to  time  added  to 
coffee,  such  as  various  starches  or  starch-containing  tissues,  which 
are  obvious  upon  microscopic  examination. 

TEA 

Tea  consists  of  the  dried  leaves  of  the  Camellia  thea^  of  which 
there  are  several  varieties. 

In  order  to  examine  the  leaves  they  should  be  soaked  in  water. 


FIG.  34 

SECTION  OF  TKA  LEAF,  SHOWING  IDIOBLASTS 

X  160.    (After  Moller) 


FIG.  33.      TEA  LEAF 
X  4.     {ad  nat.  T.G.S.) 


COCOA  131 

and  when  they  have  assumed  their  original  shape  they  may  be 
dried  between  blotting-paper  and  mounted  on  glass  in  formalin- 
gelatin  or  other  like  substances. 

The  leaf  thus  prepared  is  seen  to  be  elliptical  in  shape.  The 
margin  is  serrated  and  the  apex  of  each  serration  is  surmounted 
with  a  minute  spine.  These  serrations  do  not  extend  quite  to 
the  point  of  attachment  of  the  stalk.  The  apex  of  the  leaf  is 
slightly  emarginate.  The  ribs  come  off  from  the  midrib  nearly 
dichotomously  and  form  a  looped  network  which  extends  nearly 
but  not  quite  to  the  edge  of  the  leaf,  leaving  a  clear  margin. 

If  there  is  any  doubt  from  the  shape  of  the  leaf  as  to  its 
genuineness,  a  small  portion  should  be  cut  off  near  a  rib,  warmed 
in  a  20%  solution  of  soda  and  mounted  on  a  slide,  the  coverslip 
pressed  down  firmly  but  gently.  Upon  examining  the  specimen 
under  the  microscope  long  tough  tenacious  branched  cells  are 
seen.  These  are  termed  idioblasts,  and  do  not  occur  in  any  of 
the  leaves  likely  to  be  mistaken  for  tea  leaves. 

COCOA 

Cocoa  is  prepared  from  the  roasted  seeds  of  the  Theobroma 
cacao.  If  the  cocoa  nibs  be  finely  ground  in  a  mortar  and 
mounted   in  water,   it  will  be  found  that  there  is  so  much  fat 


b 

FIG.    35 
(a)  Parenchymatous  cells  of  the  cocoa  bean 

X   150 

{b)  Portion  of  husk,  showing  characteristic  cellular  hairs 
X  150.    (After  Rubner) 

present  that  the  tissues  will  be  seen  with  difficulty.  In  order  to 
avoid  this  the  ground  nibs  may  be  treated  with  ether  and  subse- 
quently with  warm  water,  and  mounted  in  water. 


132  MICROSCOPY 

A  second  method  is  to  warm  some  of  the  ground  nibs  in  a 
watchglass  containing  a  little  20%  soda.  Some  pieces  are  then 
mounted  in  soda.  If,  as  sometimes  happens,  the  particles  are 
not  sufficiently  soft  to  allow  the  coverslips  to  be  pressed  down 
on  to  the  specimen  they  may  be  crushed  between  two  slides 
before  mounting. 

Two  kinds  of  tissue  will  be  seen  upon  microscopic  examina- 
tion, one  the  external  covering  and  the  other  the  parenchyma. 
The  cells  of  the  external  covering  are  large  and  have  super- 
imposed "hairs"  consisting  of  thick-walled  cells  arranged  as  in 
the  illustration.  The  parenchyma  consists  of  smaller  mucilage 
cells,  some  of  which  contain  starch  granules  and  others  the 
pigment  of  the  cocoa. 

The  most  of  the  prepared  cocoas  consist  only  of  the  paren- 
chymatous cells,  with  or  without  the  addition  of  other  starch, 
and  generally  with  a  portion  of  the  fat  removed. 

Cocoa  starch  granules  are  about  the  same  size  as  rice,  but  are 
rounded  in  contour. 

The  addition  of  foreign  starches  may  be  easily  ascertained  by 
shaking  up  some  of  the  cocoa  in  cold  water,  allowing  the  coarser 
particles  to  settle,  and  mounting  some  of  the  milky  supernatant 

fluid. 

CLOTHING,    ETC. 

Under  this  heading  are  included  the  fibres  used  in  the  manu- 
facture of  clothing  ;  and  those  which  are  in  common  use  for 
other  purposes.  They  may  be  found  in  water  sediments,  milk, 
sewage  and  elsewhere ;  and  their  identification  is  frequently 
required  of  the  student  at  D.P.H.  examinations. 

A.  VEGETABLE  FIBRES 

EX  A  MI N A  TION 

All  the  vegetable  fibres  may  be  examined  under  the  microscope 
in  water. 

The  fibres  should  be  macerated  in  water  in  order  to  get  rid  of 
the  air,  and  teased  out  as  finely  as  possible.  They  may  then  be 
placed  on  a  slide  with  some  water,  and  a  coverslip  superimposed. 
The  excess  of  water  at  the  edges  of  the  coverslip  should  be 
removed  with  blotting-paper  previous  to  examination. 

Permanent  specimens  may  be  made  either  stained  or  unstained. 
The  fibres  may  be  coloured  with  any  of  the  aniline  dyes  in  weak 
solution,  for  a  few  minutes. 


CLOTHING 


133 


After  staining,  or  if  they  are  to  be  mounted  unstained,  they 
should  be  immersed  in  absolute  alcohol  for  several  minutes,  then 
removed  to  xylol  for  4  or  5  minutes,  drained  of  the  excess  of 
xylol  and  mounted  in  Canada  balsam. 

I.  Cotton 

This  is  the  downy  hair  of  the  seeds  of  plants  belonging  to  the 
family  Gossypium.  Four  species  appear  to  be  available  for  this 
purpose,  the  commonest  being  the  Gossypium  barbadense. 

Under  the  microscope  the 
fibres  are  seen  to  be  long  (from 
\  to  I  in.)  and  thin,  the  diameter 
being  about  20  or  30  /x.  They 
are  flattened  and  have  a  very 
distinct  margin  which  sometimes 
gives  the  impression  of  a  double 
contour.  The  chief  characterstic 
about  the  fibres  is  that  they  are 
all  twisted,  and  this,  however 
short  the  fibres  may  be. 

Cotton  fibre  is  largely  used  in 
the  manufacture  of  sheeting, 
calico,  towelling,  fustian,  vel- 
veteen, flannelette,  paper,  etc. 
Mixed  with  wool  it  constitutes 
merino,  which  is  used  for  vests, 
socks,  etc.  It  is  used  as  an  adulterant  of  silk,  but  not  to  such  a 
great  extent  as  is  jute. 

2.  Linen  Fibre — Flax 

Flax  consists  of  bast  fibres  and  is  obtained  from  the  stalk  of 
Linum   iisitatissijnum.     The   stalks   are    allowed   to  rot  on  the 


Fig.  Tfi.     COTTON  fibres 

X  100.    {ad  tiat.  T.G.S.) 


FIG.    37.       LINEN    FIBRES 
X  100.     (^ad.  nat.  T.G.S.) 


134 


MICROSCOPY 


ground  and  are  subsequently  beaten  and  combed,  the  result  of 
the  process  being  the  raw  flax  of  commerce. 

Under  the  microscope  the  fibres  are  about  the  same  diameter 
as  cotton,  but  are  cylindrical  (not  flat).  At  more  or  less  regular 
intervals  there  are  distinct  nodes  or  transverse  divisions,  and 
from  some  of  these  fine  hairs  (a  few  /x  long)  are  seen  to  issue. 

Flax  is  used  for  shirts,  collars,  sheeting,  and  rags  made  of 
linen  are  used  to  make  paper  of  good  quality. 

3-  Jute 

Jute  is  the  bast  fibre  of  the  Co?'chonis  capsidaris  or  Corchoms 
olitoriKs,  a  tropical  shrub  grown  chiefly  in  Bengal.  Microscopi- 
cally the  fibres  are  seen  to  be  cylindrical  and  to  have  a  central 
channel  which  varies  in  width  and  is  very  distinct.  Jute  is  used 
for  making  mats  and  sacking,  and  in  this  country  is  used  largely 
as  an  adulterant  of  silk. 

4.  Hemp 

Hemp  consists  of  the  bast  fibres  of  the  Cannabis  sativa  and 
resembles  linen  very  closely.  It  is  coarser  than  linen,  however, 
and  may  generally  be  identified  by  this  character. 

It  is  used  chiefly  for  the  manufacture  of  sacking  and  ropes,  and 
is  little  seen  as  an  article  of  clothing. 


FIG.   38.      JUTE 
X  100.    {ad  nat.  T.G.S.) 


FIG.   39.       MANILLA    HEMP 
X  100.    {ad  nat.  T.G.S.) 


CLOTHING 


135 


FIG.    40.       WOOD    FIBRICS 


5.  Coir 

Coir  is  the  coarse  fibre  obtained  from  tlie  outer  luisk  of  the 
cocoanut.  Under  the  microscope  the  fibres  are  seen  to  be  very 
coarse  and  irregular. 

It  is  used  chiefly  in  the  manufacture  of  mats  and  coarse  ropes, 
and  rarely  if  ever  is  met  with  in  clothing  in  this  country. 

Paper 

Paper  which  is  sometimes 
found  in  the  sediment  of  water 
and  which  has  been  macerated 
is  seen  to  consist  either  of  linen 
or  cotton  fibres,  or  of  wood 
fibres.  Many  toilet  papers 
are  made  from  wood  pulp. 
This  paper  macerated  in 
water  and  examined  under  the 
microscope  is  seen  to  consist 
of  fibres,  many  of  which  show 
"  spiral  cells  "  (A)  and  other 
"pitted  ducts"  {B).  x  100 

B.  ANIMAL  FIBRES 

The  following  are  best  examined  by  macerating  for  a  short 
time  in  dilute  soda  (2-5%)  and  mounting  in  water  or  dilute  soda. 

Note 

The  soda  should  not  be  used  too  strong  nor  for  too  long 
a  period,  since  wool  and  hair  are  eventually  disintegrated  and 
dissolved  by  it. 

I.  Wool 

Wool  is  the  prepared  fleece 
from  sheep  and  goats.  The 
wool  used  in  some  Jaeger 
material  is  derived  from  the 
camel. 

Under  the  microscope  the 
fibres  are  seen  to  be  cylin- 
drical and  to  be  thicker  than 
cotton  or  linen.  The  chief 
characteristic  of  wool  is  the 

FIG,  41,      WOOL  FIBRES 
X  100,    {aduat.  T,G,S.) 


136 


MICROSCOPY 


imbrication  of  the  external  scales,  which  gives  the  edge  a  ser- 
rated appearance. 

Wool  is  used  in  making  flannel,  blankets,  worsted  stockings, 
underclothing,  etc. 

2.  Silk 

Silk  is  the  fibre  produced  by  the  larvse  of  several  kinds  of 

moth,  the  Bombvx  mori,  the 
Ajitherea  yaf?iamaya,  Antherea 
Pernyi^  and  Attacus  cynthia,  to 
serve  as  a  sheath  for  the  chrysa- 
lis until  it  emerges  therefrom  as 
the  adult  moth. 

If  silk  be  mounted  in  water 
and  examined  under  the  micro- 
scope it  is  seen  to  be  quite 
structureless  and  waxy.  In  reality 
there  is  a  central  core  surrounded 
by  albuminous  material.  The 
fibres  are  smaller  than  any  of 
the  preceding,  the  diameter  being 
half  or  less  than  half  that  of 
wool.  There  are  no  nodes,  im- 
bricated scales,  or  twists. 

It  is  dissolved  by  strong  alkalis  and  acids,  even  by  acetic  acid. 


FIG.  42.      SILK    FIBRES 
X  100.    {ad  nai.  T.  G.S.) 


HUMAN   PARASITES 

Under  this  heading  are  considered  some  of  the  common 
parasites  that  infect  the  body  and  clothing  of  man.  Internal 
parasites  such  as  the  worms  and  bacteria  do  not,  for  the  most 
part,  come  within  the  scope  of  this  book  ;  but  mention  is  made, 
under  the  section  devoted  to  meat  inspection,  of  certain  of  the 
parasitic  worms  which  are  introduced  to  the  body  through  the 
ingestion  of  infected  meat.  At  present,  however,  only  those 
common  external  parasites,  likely  to  be  placed  before  an  exami- 
nation candidate,  are  considered. 


A.    INSECTA 

The   Pulex   irritans   (the   common    human    flea)    does    not 
require  much  description.    There  are  many  species  of  fleas ;  and, 


HUMAN    PARASITES 


"^1^7 


although  man  is  susceptible  to  the  attacksof  those  which  normally 
affect  the  lower  animals,  these  insects  prefer  for  the  most  part 
their  own  particular  host. 

Fleas  resemble  flies  to  some  extent;  but  they  have  only  single 
eyes  and  extremely  rudimentary  wings.  A  flea  is  provided  with 
a  proboscis  for  piercing  and  sucking. 


FIG.    43.       rULEX    IRRITANS 
X  10.    (After  Beille) 


FIG.    44.       I'ULKX    PENETRANS 
X  10.   (After  Beille) 


The  female  lays  her  dozen  eggs  about  the  floors  of  houses, 
kennels,  etc.  Six  days  in  the  summer  suffice  for  the  appearance 
of  the  worm-like  larvae,  which  are  provided  with  a  powerful  biting 
mouth.  They  live  on  particles  of  decaying  organic  matter.  They 
move  about  by  means  of  the  hooks  and  hairs  which  are  placed 
on  the  posterior  border  of  each  of  the  thirteen  rings  which  they 
possess.  At  the  end  of  1 1  days  the  larva  spins  a  cocoon  and  is 
transformed  into  a  chrysalis;  in  another  10  or  11  days  the 
chrysalis  emerges  as  the  perfect  insect. 

The  Sarcopsylla  penetrans  (chigoe)  is  nearly  allied  to  the 
last  described  and  has  a  familiar  history. 

The  adult  female  gets  from  the  ground  generally  on  to  the 
foot.  Here  she  burrows  her  way  beneath  the  skin,  holding  on 
with  her  powerful  mandibles.  Soon  after  she  has  become  para- 
sitic she  swells  up  to  twice  or  three  times  her  normal  size 
with  eggs. 

The  Gimex  lectu/an'us  (bed  bug)  is  a  small  insect,  having  a 
mouth  in  the  shape  of  a  beak  or  rostrum,  adapted  both  for  piercing 
and  sucking. 

The  adult  female  lays  about  50  white  cylindrical  eggs  in  that 
period  of  the  year  between  March  and  September.  The  eggs 
have  a  hinged  lid,  and  after  five  or  six  days  of  incubation,  the 
young   cimex   opens    the   lid   and   walks   out.     The   young  do 


138 


MICROSCOPY 


FIG.  45 

CIMEX    LECTULARIUS 

X  lo.    {ad  nat.  T.G.S.) 


not  come  to  maturity  for  lo  or  ii  months,  and  during  their 
adolescence  undergo  three  or  four  moultings.  The  young  are 
more  slender  than  the  adults  and  have  less  colour. 

The  cimex  lectularius  is  wingless :  it 
prefers  darkness  rather  than  light,  and  lives 
in  corners  and  niches.  In  the  twilight  it 
comes  out  of  its  corner  and  searches  for 
its  food  until  the  morning,  retreating  when 
the  room  grows  light.  The  young  cimex 
is  able  to  hunt  for  itself  and  is  independent 
of  the  adults. 

The  odour  associated  with  these  insects 
is  due  to  glands  situated  in  the  first  seg- 
ment of  the  abdomen — the  adult  bearing 
two,  and  the  young  three. 

The  Pediculi  are  provided  with  pierc- 
ing and  suctorial  mouth  parts.  The  mouth 
consists  of  a  soft  retractile  beak,  conical  in 
shape,  and  furnished  below  with  a  row  of 
hooks  for  attachment.  Inside  the  soft  beak  are  four  grooved  plates 
which  when  juxtaposed  form  a  membranous  tube  which  can  be 
extended  beyond  the  mouth,  and  which  is  used  for  piercing. 
The  thorax  is  small  in  comparison  with  the  size  of  the  abdomen, 
and  is  not  distinctly  divided  into  segments,  although  as  in  all 
insects  the  three  pairs  of  legs  are  all  attached  to  it. 

The  Pediculus  capitis,  as  its  name  implies,  is  chiefly  found  on 
the  hairy  scalp  and  obtains  its  food  by  piercing  the  skin  and 
sucking  the  blood.     It  is  of  yellowish  brown  colour, 
which  is  darker  at  the  edges.     The  legs  have  a  spine 
at  the  extremity  which  can  be  opposed  to  the  end  of 
the  digit.     This  enables  the  insect  to  suspend  itself. 

The  female  lays  about  50  greyish  eggs  which  are 
covered  at  the  end  with  a  hinged  lid.  The  eggs  are 
fastened  on  to  the  hair  with  chitinous  material  and 
the  hair  is  constricted  at  this  spot.  They  are  nearly 
always  fastened  on  the  hair  near  the  scalp,  so  that 
those  found  an  inch  or  so  from  the  stem  are  generally 
empty — the  young  having  been  hatched. 

The  eggs  are  hatched  in  about  a  week  and  the 
young  pediculus  opens  the  lid  and  crawls  out.  The 
young  resemble  the  adults  except  in  size,  and  undergo 
no  moulting  as  in  the  case  of  the  cimex.     In  three 


FIG.  46 
rEDICULUS 

CArrris 

X  10 
(After  Beille) 


HUMAN    PARASITES 


139 


FIG.  47.       PEDICULUS 
VESTIMENTORUM 
X  10.     (After  Beille) 


weeks   or   a    month    they   are    full   grown   and   are  able   to   re- 
produce. 
The  Pediculus  uestimentorum  or  body 

louse  is  the  same  length  as  the  head  louse, 

but  is  about  twice  as  broad.     The  colour  is 

the  same  as  that  of  the  head  louse,  but  is 

not  darker  at  the  edges.     The  head  is  more 

triangular  in  shape  than  that  of  the  head 

louse.     In  other  respects  the  resemblance  is 

almost  exact. 

The  female  lays  her  eggs,  to  the  number 

of   70  or  80,  in  the  folds  of   the  clothing, 

where  the  pediculus  lives — only  coming  on 

to  the  body  to  feed.     These  eggs  hatch  in 

about  a  fortnight  or  three  weeks  and  the 

young  pediculus  is  adult  in  another  fortnight  and  prepares  for 

egg  laying. 

The  Pediculus  pubis  differs  greatly  in  shape  from  the  precedmg 

species.  It  is  almost  triangular  and 
the  abdomen  is  less  broad  than  the 
thorax.  Between  the  two  there  is  no 
constriction.  Each  leg  carries  at  its 
free  extremity  a  definite  claw,  and 
not  merely  a  spine,  but  it  is  with  the 
posterior  pairs  that  the  insect  hooks 
itself  to  the  hairs. 

The  female  lays  10  or  12  eggs, 
which  she  attaches  to  the  hair  quite 
at  the  base.  The  development  of 
the  egg  .resembles  that  of  the  pre- 
ceding exactly. 


FIG. 


48.       PEDICULUS    PUBIS 
X  20.    (After  Beille) 


B.  ARACHNIDA 

To  this  class  belong  several  forms  of  acari  which  are  met  with 
as  human  parasites.  The  acari  as  a  class  differ  from  the  true 
insect  in  several  respects.  There  is  no  sign  of  division  between 
the  abdomen  and  thoracic  portions,  nor  is  the  abdomen  seg- 
mented ;  some  of  the  legs  are  attached  to  the  anterior,  and  the 
rest  to  the  posterior  portion  of  the  body. 

The  Sarcoptes  scabel  {Acarus  scabei)  has  an  oval  body 
bearing  four  pairs  of  legs,  two  pairs  placed  anteriorly  and  two 


140 


MICROSCOPY 


FIG.    49.       AGAR  US   SCAB  K I 
X  60.    (Semi-diagrammatic) 


postero-laterally  on  the  under  surface.  The  two  front  pairs 
terminate  in  small  suckers  and  the  posterior  pairs  in  spines. 
The  animal  is  greyish  in  colour  and  semi-transparent.     It  carries 

several  pairs  of  hairs,  the  longest  pairs 
being  on  each  side  of  the  anus. 

The  female  alone  forms  the  burrows 
which  are  characteristic  of  scabies ; 
she  lays  about  15  ovoid  eggs  in  the 
bottom  of  the  tunnel.  In  about  six  days 
these  are  hatched.  They  resemble  the 
adult  in  general  shape,  but  they  are 
completely  asexual ;  they  carry  only 
three  pairs  of  legs,  two  anteriorly  and 
one  pair  posteriorly.  In  order  to  gain 
their  liberty  they  pierce  the  vault  of 
the  tunnel,  and  so  arrive  on  the  skin. 
In  this  stage  the  larva  undergoes  two 
or  three  separate  moults.  In  the  next 
stage  it  obtains  its  fourth  pair  of  legs, 
and  those  which  subsequently  develop  into  females  are  somewhat 
larger  than  those  that  become  males.  After  the  next  moult  the 
sex  of  the  young  is  determined  and  the  females  are  considerably 
larger  than  the  males. 

The  male  is  now  adult  and  undergoes  no  further  change.  The 
adult  female  again  moults  before  she  makes  her  burrow  and  lays 
her  eggs.  The  male  is  more  agile  than  the  female  and  only 
excavates  the  skin  sufficiently  to  find  a  lodging,  where  he  may 
be  seen  as  a  little  brown  speck. 

The  intolerable  itching  which  the  presence  of  the  females  in 
the  tunnels  produces  is  probably  due  to  the  secretion  by  the 
acarus  of  a  poisonous  fluid.  This  is  only  secreted  during  the 
night  and  accounts  for  the  usual  phenomenon  that  the  itching  is 
only  noticed  when  the  patient  is  in  bed. 

The  tunnels  are  found  chiefly  about  the  hands,  genitals, 
buttocks  and  thighs,  but  may  be  found  everywhere  except  on 
the  back  of  the  head. 

In  order  to  obtain  an  acarus,  the  tunnel  should  be  torn 
up  with  a  sharp  needle,  and  the  female  picked  up  on  its 
point. 

To  examine  it,  it  may  simply  be  mounted  in  water,  or  in  5% 
potash. 

Similar  acari    affect  horses,  cattle,  cats,   etc.,  and  these    are 


WATER    SEDIMENT 


141 


occasionally  found  parasitic  on  human  beings,  but  they  prefer 
their  normal  hosts. 

The  ticks  or  Ixodes,  of  which  the  common  sheep  tick  {Ixodes 
ricinus)  is  perhaps  the  best-known  member,  are  commonly  dis- 
tributed in  nature,  and  are  occasionally  parasitic  on  man. 

They  differ  from  the  sarcopsidae  in  having  all  four  limbs  at 
the  anterior  extremity,  and  are  armed  with  a  powerful  beak. 


a 

FIG.    50.       IXODES   RICINUS 
X  3    («)  Dorsal  view  ;  (/>)  Ventral  view.     (After  Beille) 


The  female  alone  obtains  her  nourishment  from  the  animal 
upon  which  she  is  parasitic,  the  larvae  and  males  being  only 
accidental  parasites. 

The  female  grips  the  hair  or  skin  with  the  legs  and  digs  her 
beak  through  the  skin  at  right  angles.  There  she  remains  for 
several  days  until  she  is  full  of  blood.  She  then  withdraws  her 
beak  and  drops  off  to  the  ground.  If  she  is  brushed  off  whilst 
she  is  sucking,  her  beak  is  left  in  situ  and  may  be  a  source  of 
irritation.  The  larvae  have  a  similar  life-history  to  that  of  the 
Sarcopsidae. 

WATER  SEDIMENT 

The  following  classification  comprises  the  substances  that  may 
be  found  in  examining  a  water  sediment : — 


A.  Mineral  matter,  sand,  clay,  etc. 

B.  Vegetable  matter. 

Diatomaceae. 
Schizophyceae. 

Schizomycetes. 

Cyanophyceae. 


142 


Algre. 


MICROSCOPY 
Chlorophylacese. 


Fungi. 

Various  more  complex  plants,  or  their  debris. 
C.  A/iimal  matte?-. 
Protozoa. 
Crustacea. 
Spongidia. 
Various  more  complex  animals,  or  their  debris. 


^ 


FIG.    51.       DIATOMS 
X   200 

a,  surHice  view  ;  b,  side  view, 
showing  two  halves  of  frustule 


FIG.    52.       DESMIDS 
X   200 


FIG.    54.       EUGLENA   VIRIDIS 
X  300.    (After  Ehrenberg) 


7  ;j 


FIG.    53.       VORTICELLA 
X   150 


FIG.    55.       SPIROGEIRA 
X  60 


WATER   SEDIMENT 


143 


FIG.    56.       BEGGIATOA 
X  150 


FIG.    57,       VOLVOX    GLOBA'IOR 
X  eo.    (Partly  after  Cohn) 


FIG.    58.       ULOTHRIX 
(After  Dodel  Port) 


FIG.   59.       HUMAN    HAIR 
X  100.   {adnai.  T.G.S,) 


&m^^\ 


"r^SM 


FIG.  60.       dog's    HAIR 
X  100.   {adnat.  T.G.S.) 


144 


MICROSCOPY 


FIG.  6l.       cow's    HAIR 
X  loo.   {ad  nat.  T.G.S.) 


^'. 


FIG.  62.       rabbit's    hair 
X  100.    (ad7iat.  T.G.S.) 


a  b 

FIG.  63.       AMCEBA 
X    200 

{a)  Motile.         {b)  Resting 


FIG.   64.       PARAMCECIUM  COLI 
X  400.  (T.G.S.) 


FIG.  65.       DAPHNIA 


WATER   SEDIMENT 


145 


FIG.  66,      OVA   OF   VARIOUS   WORMS 
X  400.     (After  Leuchart) 


a.  Ascaris  himhricoides 

b  and  c.    Oxyuris  vermiculafis 

d.  Distoma  hepaticuvi 

e.  Distoma  lanceolattim 

f.  Trichocephalus  dispar 


g.  Anchylostoma  duodenale 
h.   Bolhriocephahis  latics 
i.    Tania  mediocanellata 
k.    Tania  soluini 
l.   Ascaris  tnystax 


10 


MEAT   INSPECTION 

The  inspection  of  meat  is  often  part  of  the  practical  examina- 
tion of  the  D.P.H.  candidate,  and  he  is  required  to  be  able  to 
decide  if  the  meat  shown  to  him  is  fit  for  human  consumption. 

Characters  of  Good  Meat 

Meat  when  good  and  fresh  should  have  a  marbled  appearance, 
due  to  streaks  of  fat  between  the  bundles  of  muscle  fibres.  The 
colour  should  be  bright  and  not  too  dark,  and  the  surface  of  the 
meat  should  be  glossy  and  not  dull.  Beef  is  always  darker  than 
mutton,  veal,  or  pork — chiefly  for  the  reason  that  sheep,  calves 
and  pigs  are  bled  more  freely  than  oxen  at  the  time  of  killing. 
The  older  the  animal,  the  darker  and  tougher  is  the  flesh.  The 
connective  tissue  should  be  glistening  and  firm.  The  diaphragm 
should  be  firm,  and  the  abdominal  and  thoracic  parietes 
should  show  no  evidence  of  adhesions  or  staining.  The  pleura 
should  be  intact.  The  bone-marrow  should  be  set  and  be  light 
red  :  the  spleen,  kidneys,  and  liver  should  be  regular,  of  a  good 
red,  and  without  variations  in  colour. 

Good  meat  is  firm  and  elastic,  and  does  not  pit  nor  crackle  on 
pressure.  It  is  juicy,  but  not  wet ;  and  the  juice  which  adheres 
to  the  fingers  should  be  of  a  bright  red  colour.  The  fat  is  hard 
and  dry,  but  feels  greasy.  The  kidneys,  spleen  and  liver  are 
firm.     All  lymphatic  glands  should  be  firm. 

The  smell  of  sound  meat  is  well  known  and  characteristic. 
In  order  to  test  this  more  efficiently,  the  meat  should  be  pierced 
with  a  clean  knife  or  skewer  in  the  direction  of  the  bone,  and 
the  implement  smelt  immediately  upon  its  withdrawal. 

Good  meat  gives  an  acid  reaction  with  litmus  paper. 

Good  meat,  when  dried  upon  a  water  bath,  does  not  lose  more 
than  75%  by  weight. 

Characters  of   Bad  Meat 

Meat  that  is  bad  is  often  soft  and  watery,  some  parts  are 
harder  than  others,  and  there  may  be  emphysematous  crackling. 

146 


CHARACTERS    OF   BAD    MEAT  147 

The  fat  may  be  liquid  or  soft,  highly  coloured  or  even  hsemor- 
rhagic.  A  deep  dark  purple  colour  is  seen  in  meat  when  the 
animal  has  died  without  being  bled,  or  when  some  pulmonary 
congestion  or  acute  septicaemia  has  affected  the  animal.  The 
lymphatic  glands  in  bad  meat  may  be  enlarged,  congested, 
haemorrhagic,  caseating  or  calcified.  The  pleura,  peritoneum,  or 
viscera  may  show  evidence  of  disease  such  as  tuberculosis.  Pus 
may  be  present  between  the  muscle  fibres.  The  carcass  may 
show  signs  of  emaciation.  The  odour  may  be  that  of  putre- 
faction, and  the  meat  may  be  alkaline  in  reaction.  In  advanced 
putrefaction  the  meat  may  become  a  greenish  tint. 

Test  for  Putrefaction.  A  mixture  is  prepared  containing 
I  part  of  HCl,  i  part  of  ether,  and  3  parts  of  alcohol.  A  few 
c.c.  of  this  are  placed  in  a  cylinder,  which  is  then  shaken  so  as 
to  distribute  the  reagent  over  the  sides  of  the  glass.  A  piece  of 
the  putrid  meat  is  suspended  by  a  wire  inside  the  cylinder. 
The  white  fames  of  ammonium  chloride  will  appear  if  the  meat  is 
in  a  state  of  putrefaction. 

Meat  may  be  unfit  for  human  consumption  from  one 
or  more  of  several  causes. 

1.  The  animal  may  have  been  suffering  from  a  disease  which 
can  be  communicated  to  man  by  ingestion  of  the  meat. 

2.  The  animal  may  have  been  suffering  from  a  disease  which, 
though  non-communicable  to  man,  may  render  the  meat  un- 
wholesome and  liable  from  its  contained  toxins  to  produce 
gastro-enteritis  in  the  consumer. 

3.  The  meat,  though  derived  from  a  healthy  animal,  may 
have  undergone  decomposition. 

4.  The  meat  may  not  be  of  the  character  stated — e.g.  horse- 
flesh may  be  sold  as  beef. 

Consideration  will  now  be  given  to  certain  diseases  of  animals, 
which  render  the  whole  or  parts  of  the  carcass  unfit  for  human 
consumption. 

Anthrax.  Anthrax  meat  rarely  comes  into  the  market.  The 
animal  afflicted  usually  dies  so  quickly  that  it  is  impossible  to 
have  it  slaughtered.  The  spleen,  liver  and  kidneys  are  engorged 
with  blood,  the  intestines  are  hnemorrhagic,  the  blood  is  fluid 
and  the  bacillus  anthracis  is  found  in  vast  quantities  in  the  blood 
and  viscera.  Of  course,  all  the  meat  from  an  anthrax- affected 
animal  must  be  destroyed — preferably  by  cremation. 

Actinomycosis  generally  affects  the  tongue,  lower  jaw,  and 
lungs.     The  tongue  is  wooden  in  consistence,  and   may  show 


148  MEAT    INSPECTION 

flattened  white  nodules  on  the  dorsum.  Occasionally  abscesses 
are  formed,  and  the  pus  contains  grey  granules  which  show 
typical  characters  of  the  "  ray  fungus  "  under  the  microscope. 
If  the  disease  is  not  widespread,  only  the  affected  parts  may  be 
removed,  and  the  remainder  of  the  carcass  passed  for  eating 
purposes. 

Tuberculosis.  It  should  be  remembered  that  tuberculosis 
in  cattle  does  not  frequently  lead  to  pus  formation.  The  tubercles 
remain  firm  and  typical  although  the  whole  body  may  be  filled 
with  the  disease.  No  part  of  the  body  is  exempt  from  tuber- 
culosis, although  the  lungs  and  lymphatic  glands  are  the  sites 
most  commonly  infected.  The  Royal  Commission  on  Tuber- 
culosis in  1898  made  the  following  recommendations  with  regard 
to  tuberculous  meat : — 

That  the  whole  carcass  should  be  condemned  if — 

1.  There  is  miliary  tuberculosis  in  both  lungs. 

2.  If  there  is  tuberculosis  of  both  pleura  and  peritoneum. 

3.  If  there  is  tuberculosis  of  the  muscles  or  of  the  lymphatic 
glands  situated  in  the  muscles. 

4.  If  tuberculosis  lesions  exist  in  any  part  of  an  emaciated 
carcass. 

And  that  the  affected  parts  o?ily  should  be  condemned  if — 
T.   The    lesions   are   confined  to   the  lungs  and  the  thoracic 
lymphatic  glands. 

2.  If  the  lesions  are  confined  to  the  liver. 

3.  If  the  lesions  are  confined  to  the  pharyngeal  lymphatic 
glands. 

4.  If  the  lesions  are  confined  to  any  combination  of  the  above  ; 
but  are  collectively  small  in  extent. 

The  Commission  further  recommends  that  the  whole  carcass 
of  a  pig  should  be  condemned  if  tuberculosis  is  present  even  to 
a  slight  degree ;  and  that  foreign  meat,  in  which  the  pleura 
has  been  "  stripped "  should  be  regarded  as  tuberculous  and 
should  be  condemned. 

Septicaemia. — In  the  flesh  of  an  animal  dead  of  septicaemia 
the  blood  is  fluid  and  extravasated  here  and  there.  The  organs 
will  be  engorged  and  the  causative  micro-organism  will  be  found 
in  the  heart  blood  and  generally  in  the  spleen.  Local  abscesses 
may  be  present;  and  the  flesh  will  not  set,  will  be  moist,  and 
appear  purple  in  colour.  Such  meat  will  decompose  rapidly. 
The  whole  carcass  must  be  condemned. 

Glanders  affects  horses,  and  not  cattle  and  sheep.     Horse- 


CHARACTERS    OF    BAD    MEAT  149 

flesh  infected  with  glanders  is  entirely  unfit  for  human  consump- 
tion, as  the  disease  is  communicable  to  man. 

Trichinosis.  Meat  affected  with  the  trichina  spiralis  is  seen 
to  be  speckled  with  minute  white  or  grey  dots  :  they  are  found 
especially  in  the  diaphragm.  The  pig  is  more  affected  than 
cattle  and  sheep.  In  order  to  examine  the  meat,  small  portions 
are  teased  out  in  dilute  potash  solution  and  examined  under  the 
low  power  of  the  microscope :  the  small  coiled  worms  are  easily 
distinguished.  An  account  of  them  is  given  later  under  the 
heading  of  Parasites  of  Meat. 

As  trichinosis  is  communicable  to  man,  the  carcass  of  the 
infected  pig  or  other  animal  must  be  condemned. 

Cysticercus.  Pigs,  cattle  and  sheep  all  suffer  from  cysti- 
cercus  :  the  younger  animals  chiefly  are  affected,  and  their  flesh 
is  found  to  be  pale  and  studded  with  small  cysts.  These  cysts 
contain  the  scolex  of  what,  in  the  second  host,  would  be  the  tape 
worm.     These  are  considered  later. 

All  meat  that  is  infected  with  cysticercus  must  be  considered 
unfit  for  human  consumption. 

Sheep  Rot  is  caused  by  the  distoma  hepaticum  invading 
the  portal  system.  In  early  stages  of  the  disease  it  is  necessary 
only  to  condemn  the  affected  liver :  later,  however,  the  animal 
may  become  jaundiced  and  oedematous ;  and  then  the  whole 
carcass  must  be  considered  as  unfit  for  food. 

The  strongylus  filaria  is  found  in  the  lungs  of  sheep.  If  the 
animal  is  not  emaciated  the  carcass  need  not  be  condemned  on 
this  account. 

Symptomatic  Anthrax  (quarter-ill,  etc.)  and  Malignant 
Oedema  are  septiccemic  diseases  caused  by  anaerobic  bacilli. 
Animals  so  affected  die  quickly.  Their  flesh  is  unfit  to  eat. 
The  symptoms  of  disease  resemble  generally  anthrax  and  other 
septicaemic  conditions,  and  the  meat  shows  the  same  general 
characteristics. 

Swine  Fever.  This  disease  is  very  severe  among  pigs  and 
is  exceedingly  infectious.  The  flesh  in  the  early  stages  of  the 
disease  shows  few  lesions ;  but  later  a  patchy  redness  of  the  skin 
appears  which  can  be  traced  down  through  the  fat  into  the  flesh. 
There  is  much  ulceration  of  the  large  intestine  and  patches  of 
congestion  or  consolidation  in  the  lungs,  liver  and  lymphatic 
glands.  The  flesh  of  a  pig  dead  from  swine  fever,  or  killed 
during  the  illness,  is  not  fit  for  human  food,  and  the  whole 
carcass  must  be  destroyed. 


I50  MEAT    INSPECTION 

Foot  and  Mouth  Disease.  The  tongue  and  mucous  mem- 
brane of  the  mouth  and  pharynx  show  vesicles  and  ulceration. 
The  feet  also  show  the  same  condition  of  ulcers  and  vesiculation, 
and  the  hoofs  may  be  loose,  or  may  even  fall  off.  The  disease  is 
very  infective,  and  the  carcasses  must  be  condemned. 

Horse-flesh  is  darker  in  colour  than  beef,  the  grain  is  more 
coarse,  and  the  fat  is  more  yellow  and  soft.  The  bones  are 
stronger  in  the  horse  than  in  the  ox,  and  have  better-marked 
ridges  for  the  insertion  of  muscles.  The  tongue  of  the  horse  is 
rounded  and  smooth :  that  of  the  ox  is  pointed  and  rough. 
The  liver  of  the  horse  has  three  large  lobes  and  one  small  one 
and  no  gall  bladder.  The  liver  of  the  ox  has  one  large  and  one 
small  lobe.  The  kidney  of  the  horse  is  heart-shaped  :  that  of 
the  ox  is  long  and  lobulated.  The  heart  of  the  ox  contains  a 
bone,  the  os  cordis ;  there  is  no  bone  in  the  heart  of  the  horse. 

Fish.  Fresh  fish  should  have  bright  gills  and  prominent  eyes, 
and  their  flesh  should  be  firmly  adherent  to  the  bones.  They 
should  not  pit  on  pressure,  nor  should  their  tails  hang  down 
unduly.     They  should  give  only  their  characteristic  smell. 

Inelasticity  of  the  flesh,  and  an  unpleasant  odour,  are  sure  signs 
of  decomposition  in  fish.  Fresh  fish  will  sink  in  water ;  bad  fish 
floats. 

Any  fish  that  is  not  quite  fresh  should  be  considered  unfit  for 
food.  Fish  decomposes  rapidly,  and  even  slightly  tainted  fish 
may  give  rise  to  very  severe  gastro-enteritis. 

Parasites  of  Meat 

Trichina  spiralis.  This  parasite  is  found  affecting  man 
almost  throughout  the  whole  world,  especially  where  much  pork, 
and  more  especially  uncooked  pork,  is  eaten. 

The  natural  host  would  appear  to  be  the  rat,  and  the  disease 
is  kept  up  in  them  owing  to  the  habit  of  eating  their  dead.  Pigs 
become  affected  by  eating  portions  of  dead  rats  or  the  refuse  of 
slaughtered  pigs,  to  which  they  frequently  have  access.  Man 
acquires  it  through  eating  trichinosed  pork. 

The  male  measures  12  to  1*5  mm.  and  the  unimpregnated 
female  1*5  to  2*0  mm. 

The  anterior  end  is  finely  pointed  and  surmounted  with  the 
punctiform  mouth. 

The  female  has  a  single  ovarian  tube  which  opens  into  the 
vagina  on  the  ventral  surface  about  two-fifths  of  the  length  of 


PARASITES    OF   MEAT 


151 


the  worm  from  the  mouth.     After  copulation  the  male  dies  and 

the  female  increases  in  size  to  3  to  4  mm. 

The  young  trichince  leave  their  shell 
while  still  in  the  uterus,  and  are  born  free, 
some  five  or  six  days  after  impregna- 
tion. Several  thousands  are  produced 
before  the  female  dies  and  is  voided. 

The  young  embryo  measures  about 
o*i  mm.  and  is  endowed  with  activity. 
Shortly  after  birth  they  pierce  the 
intestinal  wall,  cross  the  peritoneal 
cavity  by  the  connective-tissue  spaces 
and  so  reach  the  muscles  and  other 
tissues.  As  they  proceed  they  increase 
in   size,  and  signs  of  development  are 


FIG.  67.      TRICHINA  SPIRALIS 

a.  Female  voiding  complete 
embryos,     b.   Male 
X  80.    (After  Leuchart) 


FIG.    68.       TRICIIIx\A   SPIRALIS 

Larval  form  encysted  in 

muscular  fibre 

X  80.     (After  Leuchart) 


found.     At  the   end  of   10  days  or  less   they  arrive   at   their 
destination  in  the  connective-tissue  spaces  of  the  muscles,  etc. 

Their  presence  gives  rise  to  irritation  and  subsequent  prolifera- 
tion of  the  connective-tissue  cells  in  the  immediate  neighbour- 
hood. The  proliferation  on  the  one  hand,  and  the  movement  of 
the  trichina  on  the  other,  lead  eventually  to  the  formation  of  a 
cyst  and  wall.     At  the  end  of  about   18  days  the  trichina  has 


152  MEAT    INSPECTION 

increased  in  size  and  coiled  itself  up,  and  the  encystment  is 
complete. 

The  cysts  lie  with  their  long  diameter  parallel  to  the  muscle 
fibres  and  are  filled  with  clear  albuminous  fluid,  whilst  the  larval 
trichina  lies  coiled  up  but  in  contact  with  the  wall — especially 
when  alive.  It  now  measures  about  i  mm.  in  length,  and  is 
provided  with  a  mouth,  alimentary  canal  and  anus,  as  well  as 
rudimentary  sexual  organs. 

In  this  condition  it  remains  alive  sometimes  for  years,  and  is 
capable,  under  favourable  circumstances,  of  developing  fully. 
At  the  end  of  a  certain  time,  however,  if  the  flesh  of  the  host  is 
not  consumed,  fatty  and  calcareous  degeneration  sets  in  and  the 
larva  dies. 

The  affected  meat  can  be  seen  by  the  naked  eye  to  be 
"measly,"  and  in  order  to  examine  the  trichina  the  muscle  fibres 
containing  a  cyst  should  be  teased  out  gently  in  potash,  mounted 
in  potash  or  water,  and  a  coverslip  gently  pressed  down  on  the 
scrapings. 

Beautiful  specimens  can  be  obtained  by  hardening  the  tissue 
and  cutting  sections  of  it. 

Tcenia  mediocanel/ata  {Syjionym  T.  saginata^  Tceniarhynchus 
mediocanellatus).  This  is  perhaps  the  commonest  and  most 
widely  distributed  of  all  human  tape  worms.  It  is  found  in 
Europe,  Asia,  Africa,  America,  and  Australia.  In  this  country  it 
is  by  far  the  most  common,  the  Tcenia  solium  being  decidedly 
rare. 

It  measures  from  4  to  8  metres,  and  consists  of  from  1 200  to 
1300  proglottides.  Those  near  the  head  are  quite  small,  and 
gradually  enlarge  both  in  length  and  breadth  until  near  the 
middle  of  the  worm  they  measure  about  14  mm.  square,  and  are 
only  2  mm.  thick.  As  the  distal  end  is  approached  they  become 
narrower,  longer,  and  thicker.  As  they  break  away  from  the  main 
body  they  are  endowed  with  movement. 

The  head  is  somewhat  pear-shaped,  and  measures  from  i  '5  to 
2  mm.  in  breadth.  It  is  furnished  with  four  suckers,  but  has 
neither  booklets  nor  rostellum. 

The  genital  pore  of  the  proglottis  is  marginal,  and  frequently 
projects.  This  leads  to  the  uterus,  which  is  linear,  and  lies  in 
the  long  axis  of  the  worm,  and  which  has  20  or  30  lateral 
branches,  which  divide  dichotomously. 

The  eggs  are  contained  in  the  uterus,  and  when  the  proglottis 
is  ripe  consist  of  the  embryo  enclosed  in  a  shell,  which  is  thick, 


PARASITES    OF   MEAT 


153 


and  is  composed  of  innumerable  little  rods.  The  egg  is  dis- 
tinctly oval,  and  is  o'03  mm.  in  length.  The  embryo  possesses 
the  six  hooks. 

The  ox  is  generally  the  intermediate  host.  This  animal 
swallows  the  eggs,  and  the  digestive  juices  dissolve  the  envelope 
and  set  free  the  embryo,  which  promptly  bores  its  way  into  the 
muscles.     It  now  discards  its  hooks,  and  develops  the  head  at 


FIG.  71 


^-Sss^K:--- =;-':-■ 


a 
FIG.  69 

{a)      T^.NIA    MEDIOCANELLATA 
Head  X  20.   {ad nat.  T.G.S.) 

PROGLOTTIS,    SHOWING    NUMEROUS    DICHOTOMOUS 
BRANCHES   OF   THE    UTERUS 
Semi-diagrammatic 

{c)      EGG,    SHOWING    EMBRYO 
X    400 


the  opposite  end,  whilst  the  rest  of  the  body  becomes  a  small 
bladder.  The  whole  cysticercus  lies  between  the  muscular  fibres 
and  measures  from  i  cm.  in  length.  From  one  end  of  the  short 
diameter  of  the  cyst  the  head  of  the  cysticercus  may  be  made  to 
protrude  by  placing  it  in  warm  water.  It  is  seen  under  the 
microscope  to  be  an  exact  reproduction  of  the  head  and  neck  of 
the  mature  worm. 

The  cysticercus  is  not  known  in  the  human  subject. 

Man    is  infected   undoubtedly  from    eating   underdone    beef 


10^ 


154 


MEAT    INSPECTION 


affected  with  cysticerci;  quite  a  low  temperature  (50°  C.)  has  been 
found  sufficient  to  render  the  cysticerci  harmless. 

The  Tcenia  solium.  This  tape  worm  is  found  wherever  swine 
are  badly  kept  or  where  the  pork  is  improperly  cooked.  Hence 
it  is  comparatively  common  in  North  Germany,  and  uncommon 
in  this  country.  It  is  smaller  than  the  T.  medwcane/Zafa,  rarely 
measuring  4  m.  The  proglottides  resemble  those  of  the  T.  medio- 
cafiellata  in  shape  in  the  various  parts  of  the  body,  but  are 
smaller,  being  not  more  than  8  mm.  broad  in  the  broadest  part. 
The  genital  pore  is  marginal,  and  leads  to  a  Hnear  uterus  which 
has  8  or  10  lateral  branches  which  divide  dendritically. 

The  eggs  are  more  spherical  than  those  of  the  T.  mediocmiellata^ 
but  otherwise  resemble  them.  The  head  is  more  or  less  spherical 
with  a  diameter  of  i  'o  mm.  It  has  four  suckers  and  a  rostellum, 
which  can  be  protruded.  The  rostellum  carries  a  double  row  of 
booklets  numbering  28  in  all. 

The  life-history  and  cysticercus  form  is  similar  to  that  of  the 
T.  mediocanel/ata,  except  that  the  pig  is  the  intermediate  host. 

It  differs,  however,  in  that  this  cysticercus  is  occasionally  found 
in  man. 

It  is  extremely  rare  to  find  more  than  one  T.  mediocaiiellata  in 
the  same  patient,  but  numerous  cases  have  been  recorded  in 
which  two  or  more  T.  solia  have  been  found. 

Bothriocephalus  latus.  This  parasite — the  largest  met  with 
in  the  human  subject — is  not  of  very  wide  distribution.     It  is 


FIG.  72.     BOTHRIOCEPHALUS  LATUS  :  (a)  lateral,  (d)  front  view  of  head 

(  X   10) ;  {c,  d,  and  e)  proglottides  in  the  upper,  middle,  and  lower 

parts  of  the  worm  (nat.  size).     (After  Leuchart) 

found  in  people  inhabiting  the  Franco-Swiss  lakes,  the  Baltic 
shores,  Japan,  etc. 

It  measures  from  6  to  12  or  even  16  metres  in  length. 

The  proglottides  are  broad  and  short.  The  genital  pore  is  in 
the  centre  of  the  proglottis  and  not  marginal  as  in  most  others, 


PARASITES    OF   MEAT 


155 


and  the  uterus  is  rosette- shaped.  Each  segment  is  herma- 
phrodite. 

The  head  is  flattened  and  shaped  Hke  an  ohve  or  blunt  almond. 
It  has  two  lateral  suctorial  grooves  in  place  of  suckers,  and  has 
neither  rostellum  nor  hooklets. 

The  eggs  are  oval  with  a  long  diameter  of  about  0*05  mm., 
the  shell  is  simple,  brown,  and  closed  at  one  end  by  an  oper- 
culum. 

When  the  proglottides  break  away,  the  ova  do  not  contain  the 
mature  embryo  enclosed  in  a  shell  as  in  the  other  tape  worm,  but 


FIG.   73 
PROGLOTTIS  OF  BOTHRIOCEPHALUS 
LATUS,  SHOWING  ROSETTE  UTERUS 
X  4.     (After  Leuchart) 


a  b 

FIG.  74 
EGGS  OF  BOTHRIOCEPHALUS 

LATUS :    {a)   containing  em- 
bryo ;  [b)  empty 
X  200.     (After  Leuchart) 


merely   a  partially  developed  egg.     These,  in  order  to   attain 

maturity,  must  remain  in  water  for  some  time,  when  the  ripe 

embryo,  a  ciliated  six-hooked  one,   emerges  from  the  shell  by 

opening  the  operculum.     It  then    swims   about   in   the   water. 

This  is  either  eaten  by  fish,  or  by  some  animal 

which  is  subsequently  consumed  by  fish.     From 

the  intestine  of  the  fish  the  embryo  makes  its  way 

into    the    muscles,   where  it  loses  its   cilia  and 

hooklets,  and  elongates.     After  a  time  evidences 

of  the  two  suctorial  grooves  are  found  and  the 

embryo  attains  to  the  size  of  i  or  2  cm. ;  there 

is   no    cysticercus    form   as    described  in   other 

tape  worms,  the  embryo  sometimes  lying  almost 

free   between   the   muscular   fibres.     From   the 

imperfectly  cooked   or  raw  fish  the  embryo  is 

transferred    to    the   intestine   of  man,   dog,    cat,   etc.,   where   it 

develops  into  the  mature  worm. 

The  Distoma  hepaticum.  This  worm  is  exceedingly  common 
in  the  livers  of  sheep,  less  common  in  cattle,  sometimes  in  the 
horse,  rabbit,  and  even  in  man. 


FIG.  75.  FULLY 
DEVELOPED  EM- 
BRYO OF  BOTH- 
RIOCEPHALUS 
LATUS 
(After  Leuchart) 


156  MEAT    INSPECTION 

It  is  leaf-shaped  and  flat,  being  about  three  or  four  times  as  long 
as  it  is  broad,  and  varies  in  length  from  16-40  mm. 

The  worm  is  enclosed  by  a  skin  bearing  minute  spines  attached 
to  the  transparent  epidermis,  and  more  numerous  at  the  cephalic 
end.     The  true  skin  consists  of  dense  fibrous  tissue. 

It  possesses  two  suckers,  one  at  the  anterior  end,  that  com- 
municates with  the  mouth  and  pharynx,  and  the  other,  which  is 
placed  centrally  above  the  junction  of  the  upper  and  middle 
thirds,  is  blind.  These  suckers  itiier  alia  appear  to  be  used  for 
locomotion. 

Below  the  circular  pharynx  is  a  band  of  circular  muscular 
fibres  which  acts  as  a  sphincter,  and  prevents  the  regurgitation  of 
food  from  the  oesophagus,  which  is  a  short  prolongation  of  the 
pharynx,  and  divides  into  two  canals  a  little  above  the  ventral 
sucker.  These  two  canals  run  parallel  to  the  sides,  and  give  off 
a  series  of  branches  externally,  which  again  divide.  A  few  short 
branches  are  given  off  internally.  All  these  branched  tubes 
terminate  abruptly  in  the  parenchymatous  tissue,  and  have  no 
external  opening. 

The  excretory  or  water  vascular  system  consists  of  a  central 
canal,  which  extends  from  the  junction  of  the  upper  and  middle 
thirds  to  the  posterior  extremity,  where  it  terminates  in  a  small 
opening,  \\\q  foramen  caudak.  The  anterior  end  possesses  three 
distinct  branches,  two  lateral  and  one — a  small  one — mesial. 
The  main  trunk,  as  well  as  the  three  primary  branches,  all  give  off 
smaller  branches,  which  divide  dendritically  right  up  to  the  margin 
of  the  worm. 

The  worm  is  hermaphrodite.  There  is  a  genital  pore  situated 
just  above  the  ventral  sucker.  Into  this  pore  the  penis  protrudes. 
The  penis  is  lodged  in  a  pouch,  which  also  encloses  the  recepta- 
culum  seminis.  This  latter  receives  the  junction  of  the  two  vasa 
differentia,  which  are  formed  by  the  junction  of  the  seminiferous 
tubules  coming  from  the  testes. 

The  testes  are  not  globular  masses,  but  consist  of  a  large 
number  of  vermiform  tubes,  which  are  spread  out  in  the  middle 
of  the  ventral  portion  of  the  worm. 

The  orifice  of  the  vagina  is  very  small,  and  is  situated  in  the 
genital  pore  close  to  the  penis.  Just  behind  the  orifice,  the 
vagina  widens  out  into  a  uterus  which  is  much  coiled,  and  lies 
between  the  ventral  sucker  and  the  junction  of  the  upper  and 
middle  thirds  of  the  body,  i.e.  above  the  testes.  In  the  uterus 
can  be  seen  a  large  number  of  ova  in  various  stages  of  develop- 


PARASITES   OF    MEAT  157 

ment.  At  the  ovarian  end  the  uterus  suddenly  contracts,  and  is 
connected  with  a  tube  which  suddenly  bifurcates,  the  branches 
passing  laterally  across  the  body  and  suddenly  bending  down- 
wards near  the  lateral  margin,  to  which  they  run  parallel.  These 
tubes  give  off  branches  ending  in  grape-like  caecal  extremities, 
the  yolk  sacs.     These  sacs  contain  minute  nucleated  cellules. 

The  ovum  when  discharged  from  the  uterus  is  oval  and 
measures  0*14  mm.  in  length  and  o"ii  mm.  in  breadth.  It  con- 
tains a  fully  developed  embryo.  This  embryo  has  the  form  of 
a  cone,  the  anterior  end  being  flatly  convex  with  a  central 
proboscis-like  papilla,  and  is  completely  covered  with  cilia.  The 
ovum  is  conveyed  by  the  excrement  into  water  or  damp  soil,  and 
here  the  embryo  leaves  the  shell,  and  by  means  of  its  cilia  moves 
about  in  search  of  an  intermediate  host,  usually  a  mollusc  or 
crustacean.  It  bores  into  this  host,  loses  its  cilia  and  enlarges — 
forming  either  a  sporocyst  (a  hollow  sac  without  alimentary 
canal)  or  a  redia  (a  similar  structure,  but  possessing  an 
alimentary  canal). 

From  certain  germ  cells  in  the  sporocyst  or  redia,  cercarice. 
are  developed.  These,  like  the  adult  distoma,  possess  suckers 
and  alimentary  canal ;  but,  unlike  them,  they  have  no  genital 
organs,  and  have  an  active  and  powerful  tail.  When  they  are 
developed  they  leave  the  sporocyst  or  redia  and  the  body  of  the 
intermediate  host  and  become  free,  either  in  the  water  or  damp 
soil.  The  cercaria  now  either  seeks  a  second  intermediate  host 
and  becomes  encysted,  or  is  taken  up  by  the  definite  host,  where 
it  finds  its  way  into  the  bile  ducts,  intestine,  etc.,  and  rapidly 
develops  into  the  adult  hermaphrodite  worm. 


158 


MEAT   INSPECTION 


FIG.    76,       DISTOMA 

HEPATICUM 

Nat.  size.     (After  Leuchart) 


FIG.    ']^.    DISTOMA    HEPATICUM 

Left  half  showing  the  alimentarysysteni, 
right  half  showing  the  excretory  system 
(adapted) 


FIG.    7S.       EGGS   OF    THE   DISTOMA   HEPATICUM 
X    200 


FIG.    79.       FREE   SWIMMING  EMBRYO 
OF   DISTOMA   HEPATICUM 


FIG.    80.       CERCAKIA    FORM 
OF  DISTOMA   HEPATICUM 


APPENDIX 


CHEMICAL   SYMBOLS   AND  APPROXLMATE  ATOMIC 
WEIGHTS   OF   SOME   OF   THE   ELEMENTARY 

BODIES 


Aluminium 

Arsenic 

Barium 

Calcium 

Carbon 

Chlorine 

Copper . 

Hydrogen 

Iodine  . 

Iron 

Lead     . 

Magnesium 


Al 

As 

Ba 

Ca 

C 

CI 

Cu 

H 

I 

Fe 

Pb 

Mg 


27*5 

75*o 
137-0 

40*0 

I2'0 

35'5 
63-2 

I'D 

i26"6 

56-0 
206-5 

24*0 


Manganese    . 

Mn    .. 

55'o 

Mercury 

Nitrogen 

Hg    .. 

N      .. 

200*0 
14-0 

Oxygen 

Phosphorus 

Potassium 

0 

P      .. 
K     .. 

i6'o 
31-0 

39"o 

Silver     . 

Ag    .. 

108-0 

Sodium . 

Na   .. 

23-0 

Sulphur 
Tin 

S      .. 
Su    .. 

32-0 
.      ii8-o 

Zinc 

.     Zn    .. 

65-0 

WEIGHTS    AND    MEASURES 
[  square  metre  = 


I  gramme  =  15-432  grams. 
I  litre        =1000  cubic    centi- 
metres. 
35*3  fluid  ounces. 
61-027  cubic 
inches. 
I  metre      =39'37  inches. 


10764  square 
feet, 
cubic  metre    =  1000  litres. 
=  35-3  cubic 
feet, 
cubic  foot       =6-23  gallons, 
kilogram         =  2*204  pounds. 


159 


i6o 

APPE 

NDIX 

ALCOHOL   TABLES.    (After  Allen) 

Specific  gravity  taken  at  15*5°  C. 

Absolute 

Alcohol— percentage  by  weighty.  1*26  gives  percentage 

by  volume. 

Alcohol 

Alcohol 

Specific 

percentage 

Specific 

percentage 

gravity. 

by  weight. 

gravity. 

by  weight. 

•79384 

lOO'OO 

•879 

67-13 

•797 

98*97 

•882 

65-83 

•800 

98-03 

-884 

65*00 

803 

97'03 

*886 

64-13 

•806 

96*03 

-889 

62-82 

•809 

94-97 

-891 

61*92 

•812 

93-92 

-893 

61 -08 

•815 

92*81 

-896 

5983 

•817 

92*07 

•898 

58-95 

•820 

91*00 

-900 

58-05 

•823 

89*92 

■902 

57'2i 

•826 

88-76 

•905 

55-86 

•828 

87*96 

•907 

54-95 

•831 

86*8i 

-909 

54*00 

•833 

86-04 

•911 

53-13 

•836 

84-88 

•914 

5179 

•8382 

84*00 

*9i6 

50-96 

•841 

82-92 

*9i8 

50*09 

•843 

82-15 

•919 

49-24 

•846 

80*96 

*92  0 

48-96 

•848 

80-13 

*922 

48*05 

•851 

78-92 

-925 

46*91 

•853 

78*12 

•927 

46*00 

•856 

76*88 

-929 

45-09 

•858 

76-04 

-931 

43'95 

•860 

75"i4 

•933 

43*00 

•863 

73*79 

•935 

42-05 

•865 

72-96 

•937 

41-05 

•867 

72-09 

•939 

40*05 

•870 

70-84 

•941 

39*05 

•872 

70-04 

•943 

37*94 

•874 

69*21 

-945 

37-11 

•877 

67*96 

•947 

36-00 

APPENDIX 

161 

Alcohol 

Alcohol 

Specific 

percentage 

Specific 

percentage 

gravity. 

by  weight. 

gravity. 

by  weight. 

•949 

35'oo 

•977 

i5'oo 

•951 

34'o5 

•978 

14-00 

•953 

32-87 

•980 

i3'^o 

•954 

31-94 

•981 

I2-00 

•956 

31-00 

-982 

II    00 

•958 

29-87 

•983 

9-99 

•959 

28-87 

•985 

8-89 

•961 

27-93 

-986 

7*99 

•962 

26-87 

-988 

7 '02 

•964 

2586 

-989 

6*02 

•965 

25-00 

-991 

5'oi 

•966 

24-00 

-992 

4-51 

•967 

23-00 

■993 

3'49 

•969 

22-00 

'994 

3'^^ 

•970 

2I"00 

•995 

2-51 

•971 

20-00 

•996 

i'99 

•972 

19-00 

■997 

151 

•974 

18-00 

-998 

I  02 

•975 

17-00 

•999 

o'53 

•976 

i6-oo 

I'OOO 

o"oo 

INDEX 


Acarus  farincc,  122 

—  scabei,  139 
Actinomycosis,  147 
Air  Analysis,  95-10^ 

—  Carbon  Dioxide  in,  97 

—  Carbon  Monoxide  in,  100 

—  Ground,  no 

—  Noxious  Gases  in,  104 

—  Oxygen  in,  95 

—  Ozone  in,  104 
Alcohol,  Estimation  of,  90 
Algce  in  Water,  5 

Alum  in  Bread,  87 

Ammonia,  Albuminoid,    16,  37,  49, 

51 

Ammonia,  Free  and  Saline,   13,  37, 

49,  51 
Anquillula  aceti,  123 
Anthrax,  147 

—  Symptomatic,  149 
Antimony,  Test  for,  93 
Antiseptics  in  Milk,  74 
Arachnida,  139 
Arsenic,  Test  for,  93 
Aspergillus,  124 
Available  Chlorine,  «I2 

B 
Beer,  92 

—  Arsenic  in,  93 
Bleaching  Powder,  ill 
Boric  Acid,  Tests  for,  74 
Bothriocephalus  latus,  154 
Bread,  85 

—  Acidity  in,  86 

—  Alum  in,  87 
Bruchus  pisi,  122 
Butter,  75-83,  128 

—  Adulteration  of,  77 

—  Preservatives  in,  83 


Butter,  Salt  in,  77 

—  Water  in,  76 

Butter-Fat,  Specific  gravity  of,  78 

—  Insoluble  acids  in,  83 

—  Volatile  acids  in,  80 

C 

Calandra  granaria,  121 
Carliolic  Acid  Estimation,  112 
Carbon  Dioxide  in  Air,  97 
Carbon  Monoxide  in  Air,  100 
Chalk  Waters,  42 
Chicory,  88,  129 
Chlorides,  Estimation  of,  7 
Chlorine  Available,  1 1 1 
Cimex  lectularius,  137 
Claviceps  purpurea,  126 
Clothing,  132 

Coal  measures,  Water  from,  44 
Cocoa,  131 
Coffee,  87,  128 
Coir,  135 

Collection  of  water  samples,  i 
Cotton,  133 
Copper  in  Water,  28 
Copper-Zinc  Couple,  23 
Cysticercus,  149 

D 

Disinfectants,  111-115 
Distoma  hepaticum,  155 


Ergot,  85,  126 

Examinations,  Practical  work  in,  48 


Fish,  150 
Flax,  133 
Flour,  83 


162 


INDEX 


163 


Flour,  Composition  of,  S3 

—  Ergot  in,  85 

—  Gluten  in,  84 

—  Mineral  Matter  in,  85 
Foot  and  Mouth  Disease,  150 
Formalin,  Tests  for,  75 

G 

Gases  in  Water,  32 
Gluten,  Estimation  of,  84 
Greensands,  Waters  from,  43 
Ground  Air,  113 

H 

Hardness  in  Water,  Estimation  of,  9 
Hemp,  134 
Ilempel's  Bulbs,  95 
Horse-flesh,  150 
Human  Parasites,  136 


Indigo  Method,  21 

Insecta,  136 

Interpretation    of    Water    Analyses, 

35-48 
Iron  in  Water,  29 


Jute,  134 


J 


Kjeldahl's  Method,  52 

L 

Lead  in  Water,  27,  31 
Lemon  Juice,  94 
Lime  Juice,  94 
Limestone,  Water  from,  44 
Linen, 133 

M 
Meat,  146-158 

—  Bad,  147 

—  Good,  146 
Microscopy,  1 16-145 
Milk  Analysis,  65-75,  127 

—  Adulteration  of,  71 

—  Ash,  69 

—  Composition  of,  65 

—  Dirt  in,  127 


Milk  Fat,  69 

—  Preservatives  in,  73 

—  Specific  Gravity  of,  66 

—  Total  Solids,  67 
Mucor,  124 

N 

Nessler's  Reagent,  Use  of,  14 
Nitrates,  Estimation  of,  20 

—  Tests  for,  19 
Nitrites,  Estimation  of,  18 

—  Tests  for,  17 
Noxious  Gases  in  Air,  104 

O 

Oolite,  Water  from,  44 
Ova  of  Worms,  145 
Oxalic  Acid  Standard,  99 
Oxygen,  Al)Sorl)ed,  24 

—  Dissolved  in  Water,  32 

—  in  Air,  97 

P 

Paper,  134 

Parasites,  Human,  136 

—  of  Grain,  121 

—  of  Meat,  150 
Pediculi,  138 
Penicillium  glaucum,  123 
Pernosporon,  125 
Phenol  estimation,  112 
Poisonous  Gases  in  Air,  104 
Practical  Work,  Scheme  of,  48 
Puccinia  graminis,  125 

Pulex  irritans,  137 
Pulex  penetrans,  137 
Putrefaction,  Test  for,  147 


Rain  Water,  40 

Reagents,  Preparation  of,  56-65 

Reichert-Wollny  Process,  80 

Reinsch's  Test,  93 

River  Waters,  45 

Rye  Ergot,  126,  85 

Rye  Starch,  118 

S 

Salicylic  Acid,  Test  for,  74 
Sandstone,  Water  from,  44 
Sarcopsylla,  137 


1 64 

Sarcoptes  scabei,  139 
Septicemic  Meat,  148 
Sewage  Analysis,  50-56 

—  Ammonia  in,  51 

—  Chlorides  in,  50 

—  Dissolved  Oxygen  in,  52 

—  Effluents,  54 

—  Effluents,  Standards  for,  54 

—  Nitrates  in,  52 

—  Nitrites  in,  52 

—  Oxygen  absorbed  by,  52 

—  Total  Nitrogen  of,  52 

—  Total  Solids  of,  50 
Sheep  Rot,  149 
Silk,  136 

Soap,  10 

Soil,  Analysis  of,  106-109 
Spirits,  Analysis  of,  89 
Standard  Solutions,  59-65 
Starch  of  Arrowroot,  118 

Barley,  118 

Bean,  120 

Maize,  120 

Oats,  120 

Pea,  119 

Potato,  118 

Rice,  120 

Rye,  118 

Sago,  121 

Tapioca,  121 

Wheat,  1 17 

Starches,  Mounting  of,  116 
Surface  Waters,  41,  46 
Swine  Fever,  149 
Symptomatic  Anthrax,  149 


Tsenia  Mediocanellata,  152 
Tea,  130 
Ticks,  141 
Tidy's  Process,  24 
Tilletia  caries,  126 
Total  Solids  in  Water,  6 

Milk,  67 

Sewage,  50 

Trichina  spiralis,  150 
Trichinosis,  149 
Tuberculosis,  148 
Tylenchus  tritici,  122 


INDEX 


U 


Ustilago  carbo,  126 
Ustilago  segetum,  125 


V 


Valenta  Test,  79 
Vinegar,  93 

W 

Walter  Analysis,  1-50 

—  Aeration  of,  5 

—  Algce  in,  5 

—  Albuminoid  Ammonia  in,  16,  37 

—  Free  Ammonia  in,  13,  37 

—  Chlorides  in,  7,  36 

—  Collection  of  Samples,  i 

—  Colour  of,  4 

—  Copper  in,  28 

—  from  Chalk,  42,  47,  48 

Coal  Measures,  44 

Greensand,  48 

Limestone,  44 

Oolite,  44 

Sandstone,  44 

Subsoil,  42,  46,  47 

Surface,  41,  46 

—  Iron  in,  29 

—  Nitrates  in,  20,  ;8 

—  Nitrites  in,  18,  38 

—  Oxygen  absorbed  by,  24,  39 

—  Permanent  Hardness  of,  12 

—  Physical  Characters,  4,  35 

—  Rain,  40 

—  Reaction  of,  5,  36 

—  Report,  3 

—  River,  45 

—  Sediment,  5,  141 

—  Smell  of,  5 

—  Taste  of,  4 

—  Total  Hardness  of,  9,  36 

—  Total  Solids  in,  6,  35 

—  Turbidity  in,  4 

—  Volatile  Solids  in,  7 

—  Zinc  in,  30 
Wines,  Analysis  of,  91 
Winkler's  Method,  32 
Wool,  135 

Z 
Zinc  in  Water,  30 


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LIST  OF  CHEMICAL  BOOKS  5 

JOHNSTON,  J.  F.  W.  Elements  of  Agricultural  Chem- 
istry. Revised  and  lewritten  by  Charles  A.  Cameron 
and  C.  M.  Aikman.  Nineteenth  Edition.  Illustrated. 
i2mo.     cloth.     502  pp.  $2.60 

SEMBLE,  W.  P.,  and  UNDERHILL,  C.  R.  The  Periodic 
Law  and  the  Hydrogen  Spectrum.  Illustrated.  8vo. 
paper.     16  pp.  net,  $0.50 

KEMP,  J.  P.  A  Handbook  of  Rocks.  For  use  without 
the  microscope.  Eonrth  Edition  revised.  Illustrated. 
8vo.    cloth.    250  pp.  net,  $1.50 

KERSHAW,  J.  B.  C.  Fuel,  Water,  and  Gas  Analysis,  for 
Steam  Users.     50  ill.    8vo.    cloth.    178  pp.     net,  $2.50 

KOLLER,  T.  Cosmetics.  A  handbook  of  the  manufac- 
ture, employment  and  testing  of  all  cosmetic  materials 
and  cosmetic  specialties.  Translated  from  the  German 
by  Charles  Salter.     8vo.     cloth.     262  pp.       net,  $2.50 

KRATJCH,  C.  Testing  of  Chemical  Reagents  for  Purity. 
Authorized  translation  of  the  Third  Edition,  by  J.  A. 
Williamson  and  L.  W.  Dupre.  With  author's  additions 
and  emendations.    8vo.    cloth.    350  pp.  net,  $3.00 

LASSAR-COHN.  Introduction  to  Modern  Scientific 
Chemistry.  In  the  form  of  popular  lectures  suited  for 
University  Extension  students  and  general  readers. 
Translated  from  the  Second  German  Edition  by  M.  M. 
Pattison  Muir.   Illus.    i2mo.   cloth.   356  pp.  $2.00 

LUNGE,  GEORGE.  Technical  Methods  of  Chemical 
Analysis.  Translated  from  the  Second  German  Edition 
by  Charles  A.  Keane,  with  the  collaboration  of  eminent 
experts.  To  be  complete  in  three  volumes.  Vol.  I.  (in 
two  parts).  201  ill.  8vo.  cloth.  1024  pp.       net,  $15.00. 

Volumes  II.  and  III.  in  active  preparation. 


6  D.  VAN  NOSTRAND  COMPANY'S 

ITJNGE,  Q^-EO-RQ^Y..— Continued. 

Technical  Chemists'  Handbook.  Tables  and  meth- 
ods of  analysis  for  manufacturers  of  inorganic  chemi- 
cal products.    Illus.    i2mo.   leather.   276  pp.   net,  $3.50 


—  Coal,  Tar  and  Ammonia.  Fourth  and  Enlarged  Edi- 
tion. In  two  volumes,  not  sold  separately.  305  illus- 
trations.   8vo.     cloth.     1210  pp.  net,  $15.00 

—  The    Manufacture    of    Sulphuric    Acid    and   Alkali. 


A  theoretical  and  practical  treatise. 
Vol.  I.    Sulphuric  Acid.     Third  Edition,  enlarged.     In 
two  parts,  not  sold  separately.     500  illustrations.    8vo. 
cloth.     1225  pp.  net,  $15.00 

Vol.  II.  Sulphate  of  Soda,  Hydrochloric  Acid,  Leblanc 
Soda.  Third  Edition,  much  enlarged.  In  two  parts, 
not  sold  separately.  335  illustrations.  8vo.  cloth. 
1044  pp.  net,  $15.00 

Vol.  III.  Ammonia  Soda.  Various  Processes  of  Al- 
kali-making, and  the  Chlorine  Industry.  181  illus- 
trations'.    8vo.     cloth.     784  pp.  net,  $10.00 

Vol.  IV.     Electrolytical  Methods.     In  Press. 

LTJQUETJR,  L.    M.      Minerals   in   Rock   Sections.      The 

practical  methods  of  identifying  them  with  the  micro- 
scope. Third  Edition.  86  illustrations.  8vo.  cloth. 
150  pp.  net,  $1.50 

MARTIN,  G.  Triumphs  and  Wonders  of  Modern  Chem- 
istry. A  popular  treatise  on  modern  chemistry  and 
its  marvels  written  in  non-technical  language.  y6  il- 
lustrations.    i2mo.     cloth.     358  pp.  net,  $2.00 

MELICK,  CHARLES  W.  Dairy  Laboratory  Guide,  s^ 
illustrations.     i2mo.    cloth.     135  pp.  net,  $1.25 


LIST  OF  CHEMICAL  BOOKS 


MERCK,  E.  Chemical  Reagents :  Their  Purity  and  Tests. 
8vo.    cloth.    250  pp.  net,  $1.50 

MILLER,  E.  H.  Quantitative  Analysis  for  Mining  En- 
gineers.   Second  Ed.    8vo.    cloth.    158  pp.      net,  $1.50 

MOSES,  A.  J.,  and  PARSONS,  C.  L.  Elements  of  Mineral- 
ogy, Crystallography,  and  Blowpipe  Analysis  from  a 
Practical  Standpoint.  Fourth  Edition.  583  illustra- 
tions.    8vo.     cloth.     448  pp.  net,  $2.50 

MTJNBY,  A.  E.  Introduction  to  the  Chemistry  and 
Physics  of  Building  Materials.  Illus.  8vo.  cloth.  365 
pp.    (Van  Nostrand's  Westminster  Series.)     net,  $2.00 

MURRAY,  J.  A.  Soils  and  Manures.  33  illustrations. 
8vo.  cloth.  367  pp.  (Van  Nostrand's  Westminster 
Series.)  net,  $2.00 

NAQUET,  A.  Legal  Chemistry.  A  guide  to  the  detec- 
tion of  poisons  as  applied  to  chemical  jurisprudence. 
Translated,  with  additions,  from  the  French,  by  J.  P. 
Battershall.  Second  Edition^  rez'ised  zinfh  additions. 
i2mo.    cloth.     190  pp.  $2.00 

OLSEN,  J.  C.  A  Textbook  of  Quantitative  Chemical 
Analysis  by  G-ravimetric  and  Gasometric  Methods. 
Including  74  laboratory  exercises  giving  the  analysis 
of  pure  salts,  alloys,  minerals  and  technical  products. 
Fourth  Edition,  revised  and  enlarged.  74  illustrations. 
8vo.    cloth.,  576  pp.  net,  $4.00 

PARRY,  ERNEST  J.  The  Chemistry  of  Essential  Oils 
and  Artificial  Perfumes.  Second  Edition,  thoroughly 
revised  and  greatly  enlarged.  Illustrated.  8vo.  cloth. 
554  pp.  net,  $5.00 


8  D.  VAN  NOSTRAND  COMPANY'S 

PERKIN,  F.  M.  Practical  Methods  of  Inorganic  Chem- 
istry.    Illustrated.     I2mc.    cloth.     152  pp.     net,  $1.00 

PHILLIPS,  J.  Engineering  Chemistry.  A  practical 
treatise.  Comprising  methods  of  analysis  and  valua- 
tion of  the  principal  materials  used  in  engineering 
works.  Third  Edition,  revised  and  enlarged.  Illus- 
trated.    i2mo.     cloth.     422  pp.  net,  $4.50 

PLATTNER'S  Manual  of  Qualitative  and  Quantitative 
Analysis  with  the  Blowpipe.  Eighth  Edition,  revised. 
Translated  by  Henry  B.  Cornwall,  assisted  by  John 
H.  Caswell,  from  the  Sixth  German  Edition,  by  Fried- 
rich    Kolbeck.  87  ill.  8vo.  cloth.  463  pp.         net,  $4.00 

PRESCOTT,  A.  B.  Organic  Analysis.  A  manual  of  the 
descriptive  and  analytical  chemistry  of  certain  carbon 
compounds  in  common  use.  Sixth  Edition.  Illus- 
trated.    Svo.     cloth.     533  pp.  $5.00 

PRESCOTT,  A.  B.,  and  JOHNSON,  0.  C.  Qualitative 
Chemical  Analysis.  Sixth  Edition,  revised  and  en- 
larged.   Svo.    clolh.    439  pp.  net,  $3.50 

PRESCOTT,  A.  B.,  and  SULLIVAN,  E,  C.  First  Book  in 
Qualitative  Chemistry.  For  studies  of  water  solution 
and  mass  action.  Eleventh  Edition,  entirely  rewritten. 
i2mo.    cloth.    150  pp.  net,  $1.50 

PROST,  E.  Manual  of  Chemical  Analysis.  As  applied 
to  the  assay  of  fuels,  ores,  metals,  alloys,  salts,  and 
other  mineral  products.  Translated  from  the  original 
by  J.  C.  Smith.    Illus.   Svo.   cloth.   300  pp.    net,  $4.50 

PYNCHON,    T.    R.      Introduction   to    Chemical   Physics. 

Third  Edition,  revised  and  enlarged.     269  illustrations. 
Svo.    cloth.    575  pp.  $3.00 


LIST  OF  CHEMICAL  BOOKS 


ROGERS,  ALLEN.  A  Laboratory  Guide  of  Industrial 
Chemistry.  Illustrated.  8vo.   cloth.    170  pp.    net,  $1.50 

ROGERS,  ALLEN,  and  AUBERT,  ALFRED  B.    Industrial 

Chemistry.     Written  by  a  staff  of  eminent  specialists. 
8vo.     cloth.     Illustrated.  In  Press. 

ROTH,  W.  A.  Exercises  in  Physical  Chemistry.  Author- 
ized translation  by  A.  T.  Cameron.  49  illustrations. 
8vo.    cloth.    208  pp.  net,  $2.00 

SCHERER,  R.  Casein:  Its  Preparation  and  Technical 
Utilization.  Translated  from  the  German  by  Charles 
Salter.  Second  Edition,  revised  and  enlarged.  Il- 
lustrated.    8vo.    cloth.     196  pp.  net,  $3.00 

SCHWEIZER,  V.  Distillation  of  Resins,  Resinate  Lakes 
and  Pigments.  Illustrated.  8vo.  cloth.  183pp.net,  $3.50 

SCOTT,  W.  W.  Qualitative  Chemical  Analysis.  A  labo- 
ratory manual.   Illus.   8vo.   cloth.    176  pp.      net,  $1.50 

SEIDELL,  A.  Solubilities  of  Inorganic  and  Organic  Sub- 
stances. A  handbook  of  the  most  reliable  quantitative 
solubility  determinations.  Second  Printing,  corrected. 
8vo.     cloth.     367  pp.  net,  $3.00 

SENTER,  G.  Outlines  of  Physical  Chemistry.  Second 
Edition,  revised.    Illus.     i2mo.    cloth.    401  pp.    $1.75 

SEXTON,  A.  H.  Fuel  and  Refractory  Materials.  Second 
Ed.,  revised.  104  illus.  i2mo.  cloth.  374  pp.     net,  $2.00 

SMITH,    W.      The    Chemistry    of    Hat    Manufacturing. 

Revised    and    edited    by    Albert    Shonk.      Illustrated. 
i2mo.    cloth.     132  pp.  net,  $3.00 

SPEYERS,  C.  L.  Text-book  of  Physical  Chemistry.  20 
illustrations.    8vo. '  cloth.    230  pp.  net,  $2.25 


10  D.  VAl^  NOSTRAND  COMPANY'S 

STEVENS,  H.  P.  Paper  Mill  Chemist.  67  illustrations. 
82  tables.     i6nio.     cloth.     280  pp.  net,  $2.50 

SUDBOROUGH,  J.  J.,  and  JAMES,  J.  C.  Practical  Or- 
ganic Chemistry.  92  illustrations.  i2mo.  cloth. 
394  pp.  net,  $2.00 

TITHERLEY,  A.  W.  Laboratory  Course  of  Organic 
Chemistry,  Including  Qualitative  Organic  Analysis. 
Illustrated.     8vo.     cloth.    235  pp.  net,  $2.00 

TOCH,  M.     Chemistry  and  Technology  of  Mixed  Paints. 

62   photo-micrographs    and   engravings.      8vo.      cloth. 
166  pp.  net,  $3.00 

Materials  for  Permanent  Painting.  A  manual  for 

manufacturers,    art    dealers,    artists,  and    collectors. 

With    full-page    plates.      Illustrated.  i2mo.      cloth. 

208  pp.  net,  $2.00 

TUCKER,  J.  H.  A  Manual  of  Sugar  Analysis.  Sixth 
Edition.    43  illustrations.    8vo.    cloth.    353  pp.    $3.50 

VAN  NOSTRAND'S  Chemical  Annual,  Based  on  Bieder- 
mann's  "Chemiker  Kalender."  Edited  by  J.  C.  Olsen, 
with  the  co-operation  of  eminent  chemists.  Second 
Issue,   1909.     i2mo.     cloth.  net,  $2.50 

VINCENT,  C.  Ammonia  and  Its  Compounds.  Their 
manufacture  and  uses.  Translated  from  the  French 
by  M.  J.  Salter.   32  ill.   8vo.   cloth.    113  pp.     net,  $2.00 

VON  GEORGIEVICS,  G.  Chemical  Technology  of  Textile 
Fibres.  Translated  from  tlie  German  by  Charles 
Salter.  47  illustrations.   8vo.  cloth.   320  pp.    net,  $4.50 

Chemistry  of  Dyestuffs.  Translated  from  the  Sec- 
ond German  Edition  by  Charles  Salter.  8vo.  cloth. 
412  pp.  net,  $4.50 


LIST  OF  CHEMICAL  BOOKS  ii 

WANKLYN,  J.  A.  Milk  Analysis.  A  practical  treatise 
on  the  examination  of  milk  and  its  derivatives,  cream, 
butter  and  cheese.    Illus.    i2mo.    cloth.    73  pp.      $1.00 

Water  Analysis.    A  practical  treatise  on  the  exami- 


nation of  potable  water.    Eleventh  Edition,  revised^  by 
W.J.Cooper.      Illus.      i2mo.     cloth.     213  pp.      $2.00 

WINCHELL,  N.  H.  and  A.  N.  Elements  of  Optical  Min- 
eralogy. An  introduction  to  microscopic  petrography. 
350  ill.     4  plates.     8vo.     cloth.     510  pp.  $3.50 

WINKLER,  C,  and  LUNGE,  G.  Handbook  of  Technical 
Gas  Analysis.  Second  English  Edition.  Illustrated. 
8vo.     cloth.     190  pp.  $4.00 

WORDEN,  C.  E.  The  Nitrocellulose  Industry.  A  com- 
pendium of  the  history,  chemistry,  manufacture,  com- 
mercial application,  and  analysis  of  nitrates,  acetates, 
and  xanthates  of  cellulose  as  applied  to  the  peaceful 
arts.  With  a  chapter  on  gun  cotton,  smokeless  pow- 
der and  explosive  cellulose  nitrates.  Illustrated. 
8vo.    cloth.    Two  volumes.     1239  pp.  net,  $10.00 


D.  VAN  NOSTRAND  COMPANY 

Publishers  and  Booksellers 

23  HURRAY  AND  27  WARREN  STREETS,  NEW  YORK. 


SECOND  ISSUE,  1909 
12mo.  cloth     575  Pages     Net.  $2.50 

VAN  NOSTRAND'S 

Chemical  Annual 

A  HANDBOOK  OF  USEFUL  DATA 

for  analytical,  manufacturing  and  investi- 
gating chemists  and  chemical  students. 
BASED  ON  BIEDERMANN'S  "CHEMIKER    KALENDER" 

EDITED     BY 

Prof.  J.  C.  OLSEN,  A.M.,  Ph.D. 

Polytechnic  Institute  of  Brooklyn  ;  forynerly  Fellow  Johns  Hopkins 
University  /  author  of  "  Quantitative  Chemical  Analysis  " 

WITH  THE  CO-OPERATION  OF  EMINENT  CHEMISTS 


CONTENTS 

New  Tables— Phj'sical  and  Chemical  Constant  of  the  Essential  Oils  and 
Alkaloids. 

Melting  Points  and  Composition  of  the  Fusible  Alloys. 

Density  of  Carbon  Dioxide  Polenske  Values  of  Oils,  etc. 

Tables  for  the  Calculation  of  Gravimetric,  Volumetric,  and  Gas  Analyses. 

Tables  of  the  Solubility,  Boiling  and  Freezing  Points,  Speciflc  Gravity,  and 
Molecular  Weight  of  the  commonly  used  Inorganic  and  Organic  Com- 
pounds. 

Speciflc  Gravity  Tables  of  Inorganic  and  Organic  Compounds. 

Other  Physical  and  Chemical  Constants  of  Chemical  and  Technical  Pro- 
ducts. 

Conversion  Tables  of  Weights  and  Measures. 

New  Books  and  Current  T.iterat»re  of  the  Year. 


ALL    TABLES    WILL    BE    REVISED    ANNUALLY   TO    GIVE   THE 
MOST    RECENT   AND    ACCURATE    DATA 


D.  Van  Nostrand  Company 
23  Murray  and  27  Warren  Sts.,        New  YorK 


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